use two of the same toys.....don't pick the toy off the ground in front of him.when you show the toy and he drops the one in his mouth you say OUT! at this point I put the ball over my shoulder(ball on a rope)tell him SIT! the faster he sits the faster I through the ball. As he brings the ball back I say BRING! whe he comes back the game stars over, three commands at one time, all while playing ball. Timing is everything, doing it the same every time will help the dog not be confused and will learn very quickly. Bernard Flinks has a video that Ed sells that will cover this training. You will need to watch it several times. I still learn every time I watch. Good luck

Amy, to teach the out for your (I'm assuming) pet dog, start with toys that he's only somewhat interested in to teach the "out" (or drop it if that's what you say). Make it a regular training session (leash on), giving him different toys to hold in his mouth. When he has the toy in his mouth, hold a treat that he really really likes up to his nose and immediately say "out". When he drops the toy, treat and praise. Do several of these sessions until he begins to associate the word "out" with dropping the toy.

Then go to more favorite toys and do the same thing until he's solid on the out.

Unfortunately, it's hard for a dog to spit out a tissue since it sticks to their mouth, so you can't really do the out with a tissue. But since he already knows "leave it", then use that command with a tissue - hold him on a leash in front of you, favorite treat in one hand, tissue in the other. Drop a tissue behind you and say leave it. If he does, treat and BIG praise. If he goes for it, body block him until he stops going for it, treat/praise. Then progress, slowly if you have to using several sessions, to dropping the tissue to the side of you, then right in front of him. Remember the treat and praise has to be much better than the tissue.

I agree with Lance, don't try to take stuff out of his mouth, it does create conflict and he can be taught to drop things with treats. However, in an emergency with something really dangerous (not tissue) that he won't drop, press your fingers into his cheek between his lower and upper jaw, hold it there, and he'll open his mouth so you can get it.