Pertaining to this website: step 1 is definitely make sure you're confident in your knowledge of the rules. Make yourself a search thread, and if the things you're looking for don't draw interest, be willing to either change it up or just buckle up for the long wait time that it can take to get someone new and know that it's nobody's fault (that's the choice I always go with, lmao).
In approaching people: suggest ideas that take into account their F-Lists (if posted) and their search thread. Very few people like to get a PM from someone who hasn't read their carefully crafted threads and who is suggesting a focus on a kink they don't like. Or who clearly read their thread but is ignoring key points of their interests.
In general behavior: just generally be kind, be respectful, and treat others the way you would want them to treat you, I think.