(As the original thread has been deleted, I have decided to repost the info in this new thread (with relevant edits). Credit goes to the member for that original thread).
Looking to get a certain trophy and find other gamers to do that, or just looking for other gamers for a specific game? Here's what you can do:-
1. Set up or join a Gaming Session. This is the preferred way you should go about boosting. Check the schedule and join any session that suits your needs. If you can't find one, feel free to create one yourself. Be aware that the game you're trying to boost must show up on your PSNProfile or you cannot join or create sessions for that game. Also, if you have been flagged in any game here on PSNProfiles, you cannot join and create sessions at all unless you hide all of the flagged games. Here's some suggestions on how to make a Gaming Session successful:
If you've joined a session that is led by someone else, show up on time and be ready to play. Don't forget when your session takes place; write it down, set a reminder on your cell phone, whatever you need to do to remind yourself about your session.
If you're leading the session, show up on time and be ready to lead. Be proactive in sending out friend requests to people who have joined your session. Send reminders to those people so they don't forget about the session.
If you've created the session, put it on the schedule with enough advance time for people to see it. 1 day ahead of time is simply not enough time to throw together a 4 person boosting session, for example. I like to set up sessions with 1 week's notice myself.
People will flake out. If you're leading a session, take this into account. If you need 4 people to complete a session, leave some slots open for alternates to fill in in case of no shows. I personally like to have at least 2 people available to fill in this way. Make sure you communicate clearly who has first priority to get in and who is an alternate.
Gaming Sessions don't necessarily need to be a one time thing. You can utilize this system to recruit people for long term commitments that don't necessarily have a set time, are on a continuous basis, and aren't always just about boosting trophies. Use the Remarks section on your session to communicate clearly what you're looking to get out of it.
2. Check that game's section here in the forums to see if there's a Boosting Thread. Some popular games with a lot of boosting requirements, such as Minecraft and LittleBigPlanet, have a thread open where you can post what you need and people can message you to work out something. To find these threads, on the main forum page go to PlayStation Discussion, then Game Forums, then click the first letter of the game to open the forum for that letter and then find the game in the list. If you do not see a boosting thread for the game you need (and this is very important, so pay attention):
DO NOT CREATE A NEW ONE!
If you don't already see an open boosting thread for the game you want, then refer to the section above on creating and joining Gaming Sessions. Gaming Sessions, as already stated, should be your first method to use for boosting trophies. Individually created boosting threads will be locked or deleted by the site staff, and you'll be referred to the Gaming Sessions page. Save yourself some wasted time and do not create a boosting thread.
3. Post a status update canvassing for other gamers. This site has a status update feed similar to Twitter that shows up on the forum index page. Feel free to ask for assistance that way, just be aware it's a highly inefficient method. This can also be used as another way of advertising a created Gaming Session. Do not advertise a Gaming Session by creating or posting in a thread.
4. Join the PSNProfiles Community on PS4. If you have a PS4, you can join the PSNProfiles Community and canvass for boosting partners that way as well. This way is just as hit or miss as posting a status update on the website.
5. Check the Recent Players List for the game you want to boost. For each game on your PSNProfile, the is a list of Recent Players found to the right of the trophy list for that game. You can use this as a way to get in contact with other gamers through PSN to set up boosting sessions. Do this at your own risk though. There are 7 billion people on this planet, not everyone will always be particularly thrilled at being cold-contacted like that.