I have had lucid dreams a couple of times now and I was always able to control the dream - which is handy.
Anyway, one of the tips I read, was that before you sleep, you should already envision what you want to dream about.
For example, you want to swim in a bath full of soda (lame example, I know, but please bear with me -_-), then before you fall asleep, you should think 'I will get home, go to the bathroom and I will enjoy a bath full of soda. I will feel the soda against my skin and smell the sweetness of it etc.
After a while, you should be able to control your dream when you realize you're dreaming and it's even possible to dream something you want, instead of waiting for a regular dream
I hope this helps ^^;