What are some tips to help me pop my hand/finger joints back in?

Joint popping. Not sure if you are just cracking your knuckles, which you should not overdue, or you're talking about actual joint subluxation/dislocation which implies an unstable joint. This should be checked out. In certain joints like the so-called basal joint of the thumb it is not unusual for this to be "out of joint" with arthritis. But with other joints it would be very abnormal to be chronically "out".
Depends. I am assuming that you are talking about a finger dislocation. The technique for reducing dislocations of the fingers depends on if it is a volar or dorsal dislocation. Brute force trying to pull the finger back into place may cause damage to the cartilage so unless you know what you are doing let the trainer or er doc do it if avalilable.