I'm assuming you know where to catch him because you're question says "how".
Strategy: You're first priority should be paralyzing him. Thunder wave is probably the best move for this but if you need to do extra damage Thunderbolt or any damaging paralyzing move will help. Be careful, he knows rest which will get rid of the paralysis so once he's paralyzed bring in your attacker. Ice does good damage but just make sure you don't do too much damage. He is on lvl 70 so that shouldn't be too much of a problem. Don't use an attacker with low defense or special defense because Rayquaza would cream them. Wait for him to have miniscule health left and then throw balls like mad!
Ball choice: Ultra balls are probably the best choice for this match (because you really should save your master ball for latios) but timer balls could work too (the match would have to have gone for like 50 turns for them to be useful though...). About 50 balls should do.
Items: Yes you will probably need some revive's and full restore. 10 of each to be safe, Rayquaza can really lay down a beating!
Pokemon choice: I've found Swampert is incredibly useful for this task if he's around the 55 mark and knows Ice Beam(but don't restart your game if you didn't choose him!). Any high atk/SPatk and high def/SPdef Pokemon would be handy although I don't recommend dragon types because he's knows dragon claw.
I can't really think of anything else to tell you...whoa...I wrote more here than on my last English essay! Hope that heps!
Raquaza can be found on Sky Pillar (route 131, east of pacificlodge town).
sky pillar
no
first of all you get groudon not rayqaza that's emerald and you get him near the eighth gym
you cant you can only migrate it (this is coming from a little 3rd grader.)
you cant catch a man in Pokemon ruby
no you can catch a charizard in pokemon ruby you can get it as a kanto starter
you can't catch seviper on Pokemon ruby (Pokemon sapphire only)
you cheat or you get Pokemon ruby, Sapphire, or emerald and download them onto your d.s, d.s lite, or d.s.i game. o and by the way, its spelled rayquaza.
Rayquaza is located in Sky Pillar, which is on the water route to the right of Pacifidlog Town. You can only catch it after the Elite Four.
raikou cannot be caught on Pokemon ruby
Groudon is not available in Sapphire. You have to trade it from Pokemon Ruby, and there is only one Groudon in the whole Ruby game.you cannot catch groudon in sapphire, but you can have it by transfering it from Pokemon ruby or from Pokemon emeraldyou cannot catch groudon in sapphire, but you can have it by transfering it from Pokemon ruby or from Pokemon emerald
there no cheat to catch mew in pokemon ruby
You have to catch 151 pokemon to complete the pokedex.