First buy 20 max repels and 10 great ballsand maybe 10 ultraballs Also have a pokemon that knows surf and rock smash and strength.

A common misconception is that all legendary pokemon are hard to catch. This is NOT the case for Palkia/Dialga.

Inside of the south side of Mt. Coronet (by Route 208), use Surf to cross the northern body of water and then use Rock Climb to climb the rocks.

Upstairs, you can find a Max Potion on your way to the west up the stairs,
along with an Ether in the nearby rock. An Escape Rope is on the very south
side of the continued path, although you'll want to take the stairs going up
onto the elevated area. There's an exit in the southwest corner of the room
that will take you outside to the west side of Route 207, where you can use
Rock Climb to access an Iron. TM80 (Rock Slide) can be found by crossing the
bridge, then taking the southernly route to reach it. A Revive can be found by
taking the northern route instead.

Near the very back of the cave, you'll find an opening in the wall (however,
if you have not done the events in the Veilstone Galactic Building and are
coming here for loot immediately after getting Rock Climb, this opening will
be sealed with depictions of the Legendary Trio, similar to the gate in
Celestic Town). Enter it, and then make your way up the stairs.

The stairs to the right lead to a hidden Max Revive inside of the southern
rock. Otherwise, just keep heading north.
As you enter, you'll see a familiar sight: snow. Blinding snow. Like the
Routes on your way to Snowpoint City, it is snowing at the peak of Mt.
Coronet, and the weather will be Hail inside of each battle.

This section sometimes confuses people, because there are lots of areas to
explore on the peak and I like to cover them all, so I'm going to list here
a quick-'n-easy path to take to get straight to business:

1. Head east, north, use Rock Climb.
2. Go west, south, a bit more west, and head north into the cave.
3. Use Rock Climb and follow the path in the cave east to the exit.
4. Climb down the stairs in the peak and then use Rock Climb in the chasm
to climb the western rocks.
5. Keep heading west until you get to a cave.
6. It's straightforward from here on in, so just keep following the path
and you'll get there.

But, if you want to explore everything, I have the original, slow-'n-detailed
version intact.

Head east, then north (taking the elevated path if you wish to avoid random
encounters). Use Rock Climb to climb the rocks. You can use Rock Climb again
if you wish to find a patch of grass with a rock in the middle of it. Hidden
in the rock is a Nugget.

The cave to the right of where you used Rock Climb has a giant lake in it with
a waterfall (that you'll have to explore later), as well as a PP Up and Ultra
Ball hidden inside of some of the more obvious-placed rocks.

Back to where you used Rock Climb the first time, head west. If you have a
Pokemon with Strength, you can avoid the patches of tall grass by using it on
taking the more eastern path. Otherwise, you'll need to wade through a large
field of tall grass. On the southern path, hidden inside of a rock past a rock
that you can use Rock Smash on is a Max Potion. Make your way north and into
the cave.
Inside of the cave, use Rock Climb to climb your way up to a Team Galactic
Grunt. Fight him, and then continue along until you have to fight another one.
On the very east side of the cave, you'll find an exit leading back outside.

Head north, and then down into the crevice. There's a cave down there, as well
as a few Grunts, although you won't be able to proceed deeper into the cave
until Team Galactic is off of the mountain, so you can ignore that cave if you
wish. (After they leave, come back to this entrance and you can snag yourself
TM02 (Dragon Claw), as well as exit to the northern part of the mountain.) So,
instead, use Rock Climb to get yourself up onto the western cliff. Again, if
you have a Pokemon that can use Strength, you will be able to use Strength on
the boulders to fight less Pokemon on your way to the west. Regardless of if
you have it or not, you'll want to head to the west until you find another
entrance into the mountain.

Back inside, you will find a path leading to stairs. Climb the stairs, and
then fight the two Grunts on the next floor. Keep going, and you'll find
another flight of stairs. Upstairs, you'll find another Grunt. Fight the
Grunt, and then keep going north until you reach an exit leading out.


You will now be on the very top of the Mt. Coronet, amidst the ancient ruins
known as the Spear Pillar. Fight the two Grunts guarding the entrance in a
Double Battle, and then head north a bit to see a dangerous sight... Mars,
Jupiter, and Cyrus!

After some intense dialogue, Cyrus will proceed to awaken Dialga (or, if
you're playing Pokemon Pearl, Palkia) in the most AMAZING scene ever in the
history of Pokemon games (at least, that's what I think). Save your game and
heal your Pokemon, because you're about to enter a pretty challenging fight.
When you're ready, step north, and Mars and Jupiter will challenge you to a
fight. Just then, Rival will rush in to help you out, eager to get his revenge
on Jupiter from their battle in Lake Acuity earlierMunchlax, unfortunately, is not that helpful. It knows Metal Sound, Stockpile,
Body Slam, and Swallow. However, there is a good way to get some more use out
of Rival: Knock Out his Munchlax! Unlike previous partners, whenever Rival
loses one of his Pokemon, he'll replace it with the next Pokemon on his
roster. Any of his Pokemon will be more helpful than Munchlax, so try and
Knock Out Munchlax whenever you're able to. This is one of the things that
makes this fight a bit of a challenge: at times, it will seem like a 1 vs 2
battle since Rival has horrible judgement when using moves.

Mars and Jupiter rely heavily on annoying you. Their Bronzors are able to use
Light Screen and Reflect to reduce the damage you deal, and they can use
Confuse Ray to Confuse your Pokemon. Their damaging attacks will be welcomed
compared to their constant annoyances, so try and deal with them as quickly as
possible so they have minimal impact. Fire-type attacks are your best bet,
although Water-, Fighting-, and Dark-type attacks will also do well.

Mars' Purugly is still a threat, particularly after gaining a few levels
since the last time you fought it. Its Slash attack will probably inflict a
lot of damage, so try and hit Purugly with a strong Fighting-type attack to
render it incapible of fighting as soon as you're able to. Just watch out,
because it will have the added support of the Bronzors or whichever other
Pokemon is out.

Jupiter's Skuntank is rough as always. It has Flamethrower in its roster, so
be careful with any of your Steel-type Pokemon. Just handle it the best you
can.

Although their Golbats are last in line, they are also very annoying, able to
Confuse and Poison you as well as use Mean Look to prevent you from switching
your Pokemon. One of the Golbats knows Sludge Bomb while the other knows
Poison Fang. Fortunately they're easier to take down than the Bronzors.

A great strategy to use on these two is to target only one of them, leaving
one's Bronzor out while you focus your attacks on the other Commander's
Pokemon. This way you won't have to deal with two powerful Pokemon at once.
However, you'll have to put up with the annoyances of the Bronzor.

After beating the two ladies, Rival will heal your Pokemon and will then run
off. Now its just you, Cyrus, and one angry Time Ruler Pokemon (Space Ruler in
Pearl, obviously).

Cyrus will instruct Dialga to begin using its power to take over/destroy the
world, but just then, your little pixie friends, the Legendary Trio, will
appear and will stop Dialga from unleashing its true force.
Cyrus' Pokemon have gotten much stronger since the last time you fought
against them. They've all been evolved to their final stages, gained 5 or 6
Levels, and he's even added a Gyarados to his line up.

His Honchkrow has high Attack, Special Attack, and even pretty nice HP, so be
wary of its attacks. Use Rock-, Electric-, or Ice-type attacks against it to
do the most damage.

You should be familliar with fighting Gyarados by now, so just use the regular
tactics against it. Electric-type attacks are its bane.

Weavile is very fast and very strong. It has just a little less Attack than
Honchkrow, but a tremendous amount more Speed. It knows Scissor Cross, which
is a high-power Bug-type move.

Last up is Cyrus' Crobat. It is the fastest of all of his Pokemon, and it is
capable of using Confuse Ray, Air Slash, Bite, and Cross Poison.

After beating Cyrus, he and the other Commanders will leave. Shortly
thereafter, Professor Rowan and Dawn will arrive and tell you that you have to
beat (or catch) Dialga (or Palkia in Pearl) in order to save the world.
Drastic? You know it! There's no turning back now. Save your game, and get
ready to fight against the Time (or Space) Ruler Pokemon!
DO NOT USE YOUR MASTER BALL ON DIALGA OR PALKIA! They are actually very easy
to catch in comparison to other Legendary Pokemon. Save it for either Mesprit
or Cresselia later on.

Dialga (or Palkia, although I'm just going to say Dialga for right now) will
be the strongest wild Pokemon you've encountered. It has diverse types, making
few attacks effective against it. It also will have over 100 in every stat, as
well as over 150 Special Attack, making its attacks quite painful to endure.
Its signature move, Roar of Time, is a Dragon-type Hyper Beam that will
inflict massive damage on the target but will render Dialga unable to attack
during the next turn. All of its moves are offensive moves, so expect a hit
every single turn, except for the turn after it uses Roar of Time. Don't use
your strongest attacks on Dialga if you have intentions of catching it;
instead, just whittle away at its HP, using Hyper Potions when your HP gets
low and tossing the Balls whenever you get the chance. If
you accidentally knock it out, just reset and try again. Opening up the fight
with a Quick Ball or two might also prove to be effective.

After stopping Dialga (by either beating it or catching it), Rowan and Dawn
will come over and congratulate you on your victory. Dawn will then lead you
back to where you entered the ruins as Rowan says something alone.

Before leaving, return to the spot where you fought Dialga except keep going
north and you'll find an Adamant Orb, which will boost the potency of Dialga.
(In Pearl, you will pick up the Lustrous Orb, which pretty much does the same
thing for Palkia.)

note: I definitely caught my Dialga with a great ball...Just remember to get the health down to quarter of a millimetre in the red zone and you should be fine. Dialga and Palkia both have excellent stats, yet very easy to catch. =]