Geez, we all know stories of people who have a thing with their personal trainer. do you have a standard way of turning them down, or do you just go with the flow?

Get over yourself. if you find something offensive say it.

Tell them you're gay, and that you're not interested.

Turn 'em down, they go crrazzzyyy.
Haha I'm a woman, I should know

I tell them I'm gay.

very subtly cause u don't want to upset them either… u can say something like oh ye I'm taking my gf out to dinner tonight and making little comments that you are in a committed relationship and most of all ur happy in that relationship

Tell them straight out Your GAY..lol.
Seriously, tell them you are Not interested and although you are flattered, you Don't go with Married People. be Straightforward, its the only thing that works and if that doesn't work, Move them to a new Trainer.

I'll swap jobs with yeh

tell her that she is married and you will not have anything like that. if it does not work tell her to find a new personal trainer.

Yeah, it works both ways – I've had married male clients (and yes, one or 2 female) hit on me, too, even when I wear my wedding ring. I just ignore it, but a couple of times, I've had to make it clear that we have a professional relationship and it doesn't go beyond that. (I actually once had a guy offer to pay me to be his personal trainer so I could violate "those stupid ethics rules." Yeah, NO.)

The part I hate the most is how it introduces this weird vibe into the trainer/client relationship. with most, once you've made it clear, they're totally cool, but once or twice I've given my client to another trainer b/c he was just being too weird about the whole thing. I'm there to help you get fit, not slumming for dates!

I've found that most trainers will "non-chalantly" say that they will be doing something with their girlfriend/ boyfriend on the weekend, during your first session. It's kind of funny sometimes because I'm just sitting there like, um okay, I wasn't hitting on you, but that's nice. I have to admit though, they are pretty damn hot, however, they're more of something to look at, rather than someone you want at home yelling at you to do squats.

A simple "I don't mix business with pleasure", "let's keep our relationship professional" or "I'm not interested" should do it.