Well my dreams generally involve something that happened the day before, but not a major event, something minuscule. Can I control my dreams? No, can I predict them? Somewhat.
One thing I can do is wake myself up during a dream. During a nightmare, generally before the climax (ie the scariest part) would occur, my character in the dream generally has my natural thoughts, I can say to myself "It's a dream, you should wake up now." And I open my eyes, simple as that, sometimes its in the morning, so I think it may be natural, but sometimes it is in the middle of the night when I wake up. So it all depends really. I'm not sure if anyone can really gain full control of their dreams, you should enjoy them though. I think to myself, if I were offered complete control, would I take it or not? I tend to be tested in my dreams, there is generally some sort of action I have to overcome, some fighting or a problem. So in a way I feel I'm tested in my dreams, I wouldn't want to take that away. Not to mention, my dreams really give me a lot of ideas for my Fan Fic, if I could control my dreams, I wouldn't have access to the new scenarios!