well firstly you have to catch kyogre and groudon, then at fall city(i think..)the ranger leader will be standing outside and will ask you if you want to work out what the shadows are at the temple say yes and you will go to the temple to find rayquaza(when you get to the shut gate and the slabs rise up you'll have to catch ralts, kirlia and gardevour and put them on the slabs)
p.s hope this helped =D
Edit: Actually its wintown.
Twilightpokemon
there are 26 floors ,then you have to go up 9 more floors to see RAYQUAZA!!!!! Hes talking about sky peak not sky stairway!!! These two above me are both wrong!! You don't meet Rayquaza on sky peak. They are referring to sky stairway. You meet Shaymin N0T Rayquaza!!!!
You can find Rayquaza at Sky Pillar, which is west of Pacifidlog Town. You have to beat the Elite 4 before you can battle Rayquaza.
go to the bottom floor of the guide
go to sky pillar near on pacifilog town use surf and find the tower go inside youl catch reyquaza inside
You can find it as a TM in Steam Cave. I did.
Go to the top of Sky Stairway(the place where you go to get the Sky Melodica)and defeat Rayquaza until you recruit him.
250-300hp
In Sky Staircase, there are 50 floors, but Rayquaza is EXTREMELEY hard to recruit.
At the Sky Pillar.
sky pillar
Rayquaza, Latias, or Latios
Sky pillar.
Sootopolis city, were Kyogre and Groudon are rampaging.
If Rayquaza flee'd from the Sky Pillar in Ruby/Sapphire there is no way to get another chance to fight him.
On top of Sky Pillar.
It is not necessary to catch Rayquaza. It's an optional legendary Pokemon that you can find at Sky Pillar.
You can find recruitable Gastly and its evolutions in Sky Stairway.