Look on pinterest. There are different cuts. But truth be told mine haven't seen the light of day in ages, you can't really wear them with boots, ankle boots perhaps but I prefer mine with oxfords or flats...and the last thing I want right now is exposed ankles.
To answer your question more specifically, my favorites are worn low (actually they sit on my hip bone, or slightly below) and I roll the cuff depending on my footwear. Never without cuffing. The legs can be a little loose or a lot loose, I guess depending on the cut of the jean and the width of your legs.
The concept of boyfriend jeans originally implied a young, usually slim woman who is wearing her boyfriend's jeans, and therefore one expects the fit to be oversized. Hence the usual low-on-the-hip hang, loose leg, and rolled cuff. But there are a lot of variations on the theme these days.
I've never been able to wear "boyfriend" jeans because there's too much of me, so they're never oversized. Heh.
BTW, @meandtheboys , I thought those were boyfriend jeans you were wearing at lunch the other day because what I could see of the legs looked a little roomy and they were cuffed.
The legs can be slim. But if they're boyfriend the crotch area is generally, Uhm, Kind of droopy. If you bought a pair take a look at the vendor online. You should find a pic of them on a model or something for comparison.
I can't seem to make them work for me. I figure if I have to work hard to figure it out then they probably arent the right cut for my shape. This trend shall pass me by. However, the pleated, drapey pants trend seems to be something I can pull off without effort, so I'll go with that as far as this year's trend goes.
I once tried my girlfriend's sweater and there was something not right with the collar, almost like it was meant to fit two heads through it ... I'm not trying her jeans ...
P.S. I wish there was a "Fashion" category.