i need help catching rqaquaza

I had heaps of trouble too, half of catching Rayquaza is basically luck, but to make sure you get the best chance possible of catching it than you must give it an inflictment. By this, I mean you should try to freeze it, or put Rayquaza to sleep. For this you must use an attack such as hypnosis. Also make sure it's at the lowest possible hp. Other things than can help are try having a Pokemon with a higher level out, when throwing the pokeball, and making sure the Pokemon out has a much more hp than Rayquaza when throwing the pokeball. With these tips I ended up catching mine with a regular pokeball, but that was pure luck. Hope I helped, be sure to tell me how you go.
Goal machine.

Try to cath him while he flys even thogh it looks like nothing is bieng caught.

I am a prodigy helping you. To catch rayquaza.. First go buy 30-40 timer balls. Not ultraball..
Timerballs can be bought at the mart in rustboro city.
Weaken rayquaza first in other words put it's life to RED ZONE.
Then as goal machine said you must use confusion or other attacks that can seal the rayquaza. Like sleep powder. Then keep on using timer ball or repeat ball.. Better use repeat ball. But you can also buy it.
If you really can't catch rayquaza use masterball. If you don't have tell me I have a code on infinite masterballs.. HOPE THIS HELPS!