Murfie's right, something as personal as your patron deities can/should be discovered by yourself doing some soul searching.
There's many methods to figure out who you should work with, whatever you choose it involves some amount of soul searching. Is there a culture you've always been interested in? Research their deities, or say you want to worship a deity of healing, research all deities associated with healing. If neither appeal to you, look into your own cultural heritage, and research it. Whatever you choose to narrow the list, you should see a deity that interests you or 'feels right', then look into that deity further. Once you feel you found the right one, leave out some offerings and ask him/her to accept you as a student. Wait for an answer. It could be any number of ways. If you receive no answer after a month, move on and return later. If it's a no, stop, don't press the issue [wouldn't want to make a god mad at you]