That's tricky to learn. Necessity makes it easier tho (been there). Controlling your dream is not quite what you may be thinking. You can't make it play out as if it were scripted, but rather you just kinda steer it in the direction you want depending on what's happening. With true nightmares they're hard to alter, you usually end up having to just stop them by forcing yourself completely awake. It works tho because once you fall back asleep they usually don't start up again.
I'll try anything to get rid of the stupid tornado nightmares I have. I've had them for as long as I can remember. Funny thing is, I think tornadoes are cool (cept when they destroy peoples homes) I don't get it.
I used to be able to concentrate on a certain subject right before I fell asleep, and I would dream of that person. I've done it a number of times, but the tricky thing is to think about whatever you wanna dream about exactly before you fall asleep. Gets harder as you have more things to worry about in your life.
I had a Taker dream 2 nights ago. Well, I didn't see him per say. I was at a show, sitting next to the ramp and something was going on between Austin and McMahon, and I remember saying "yeah, the past is back" or something like that. And I was thinking "takers next. i'm finally gonna see him like that" (meaning 1999) but the dream stopped before he came out. Guess I got too excited, lol!