i always have trouble doing this thing and i always wanted to know how to do it well.

from what position

side mount and in my gaurd please.

I know the basics. If you wanna get his right arm, loop your right arm over his arm (not in the armpitt). Then take your left arm and grab his wrist with it. Then clasp onto the left arm with your right hand and push upwards (from guard) or downwards (from sidemount). Use your hips to control him in the guard

cool

If you are holding the guard, same thing submission wolf said and crank the arm towards your opponents head instead of cranking it behing his back.

scorpion

You need to get your knee up high on the side that your attacking and get your hips out if you're doing it from the guard

It's easier to slap on from the mount than from the guard. Just grab the opposite wrist of your opponent, loop your arm over your opponent's triceps, grab your own wrist, and yank up til his shoulder starts popping out!