Sometimes the best ways are to find someone working the same bodypart and ask if you can work in with them. The best method I used to do was to ask someone for a spot, then introduce yourself and thank them. Nowadays, people come up to me and ask what the fuck I'm doing, and what's my current cycle.
Now I know about 80% of my gym.
The best advice I can give is to find someone who has around the same strength levels or is the same size as you. Over time you can make it a competition of whose balls are bigger. I had to point this out because there's been a lot of times in the past when after I did a heavy set, I would have to take all the weight off for my buddy, then stack it back on, so on and so forth. It can really keep the motivation down when you're spending too much time loading and unloading weights.