It's tough, and so many rescues look for different things. I was disqualified once because I give Tank holistic meds instead of your run of the mill flea, tick, and heart worm meds.
Most of the local rescues around my state like a solid vetting history, everything up to date as far as shots and heart worm tests, etc. They want all current dogs to be spayed/neutered, and they want a stable environment, fenced backyard, not much home alone time for the dog.
Those are just some of the things I can think of but I've seen places that won't adopt to people with small kids or people with newer pets.
There are so many rules and it can be frustrating, the waiting is one of the worst parts. My best advice is to keep an app on file with a rescue even if they don't have a dog you want. They will get ahold of you if they think they have a good match. Plus it lets them know you are serious and not making a decision on the fly about adoption. Make sure you also contact them often when a dog does catch your eye.
Good luck and try not to be discouraged. It will happen