Tips from myself would be;
1 - Give them as much space as you can provide. You will want to leave them to it while breeding so the more room the better as you won't be making them come out every day. If you can get an aviary up or at least an indoor aviary even better!
2 - Provide plenty of enrichment. For some reason, a lot of breeders don't give their birds anything. Whether they think it'll distract birds from breeding I don't know, but I can assure you it doesn't and the birds will enjoy playing with toys and such. You may even find that some shredding and wooden toys end up as nesting materials as my Alexandrine parakeets have proven to me
3 - Get yourself an aluminium framed nest box. They will chew the corners to bits if you aren't careful. I know greys aren't overly destructive birds compared to some species but regardless, you won't want to keep replacing boxes!
4 - Have everything you could possibly need well before you breed them. If you're parent raising you will still need emergency supplies. Stock up on formula and syringes, critical care type formula and/or electrolyte mixes. If you can, buy yourself a decent incubator and brooder. If you can't, you can make your own quite easily (at least a brooder anyway)
5 - Feed your pair good food and you will see a huge difference in health, behaviour, production and chick quality. I am not a pellet fan. The more natural the better. Try to cover all bases and they will thrive
Where abouts in the world are you? I'm sure we could help you source a pair