Well, I do not have an official binder. But I'll talk about what I do in terms of home made techniques.
Bra size: I'm an A cup.
For A cup people, a binder, in my opinion, is almost unnecessary. I use tank tops. In these pictures, I have a gray tank that I got at the Gap in the women's section over a black tank with a build in strapless bra portion in it. I got that one in the girl's section, I think. Maybe women's. Stuff that is built for my body (which, I can no longer deny it, is female) seems to work better. In reality, my chest is more pointy than in is big, so the size is not being greatly reduced. It's just smoothing it down so it doesn't poke out and making "bumps."
Frack, just look at that figure. Ugh, lol. Oh, I lowered my pants a little so the tank top was easier to see. I usually tuck it in. Sorry about the nippleage if that offends anyone.
As you can probably tell, it isn't 100% effective. However, it does look better with a t-shirt over it.
You'll want to use a binder if looking perfectly flat is you're priority. This, however, is a lot more comfortable.
Another technique, of which I have no pictures of, is taking a pair of pantyhose and cutting a hole in the crotch for your head. Cut the legs off for sleeves. It works pretty well, but I found that it made me sweat a lot.
