|Hint: It's this one.|
A good training partner is a special thing. They need to be someone you can trust, as they will often be the one spotting you. They also need to be as responsible as yourself, because getting to the gym and waiting for them for 45 minutes is not conducive to a good session. You need to have a good relationship with them, but best friends often don't make good training partners because you spend all your time dicking around. They should be at a similar level as yourself, but most people should strive to have a training partner who is ahead of them. You want someone who knows how to push you and call you out on bullshit, but also knows when enough is enough.
|Arnold and Franco: famous buddies.|
A good personal trainer should act as your training buddy. Just because we aren't doing the exercises along with you doesn't mean we aren't involved. I'm there to make sure your program is on point with your goals. I'm there to call your bullshit when you try to find a way to get out of doing front squats. I'm there to tell you that you really did have 2 more reps in you, or that you need to drop the bar right now before your spleen comes shooting out of your back.
Whether it's a training partner or a personal trainer, make sure you surround yourself with quality people. A's get with A's. Find the partner that fits with you, and go lift something heavy!
EDIT: Training partners don't always have to be participating in the program that you are doing. One of my favorite training partners was my friend Ali, who was doing her own program. We just lifted at the same time every day, thus being able to maintain a really great partnership. I'm pretty sure she totally wanted to make out with me, too.