With Guile (and to my knowledge, it only works on the original arcade SF2) you need to be right next to someone so it helps if they are in the dazed mode with stars over their head. Crouch down like you're going to do the flash kick then quickly press up on the joystick but also press medium punch and kick in that order quickly. Guile will do what looks like a throw for a second, then you are stuck together with the other person. It's totally pointless really because you can't hit them while they are stuck to you. The only way out is to do in the air throw. If you can't do that before the time runs out, you literally have to reset the whole damn game.
Air throw can be done at any time and will knock the person down even if they are all the way across the screen, it's also pretty hard to do though. Hold back on the joystick then forward then back again then press fierce punch and kick at the same time.