When we say we "want" something, or that we want to "do something", it's usually because we know exactly what it is we are asking for. This might sound silly but, ..I want a horse (no really- I'm not kidding). I can truly say that this is what I want because I know: how to take care of horses, I have the finances to afford the care, I have the property a horse needs to be comfortable, etc. In essence, I have thought about everything that my decision entails and have concluded I am able to deal with what comes along with it, and would still like to go through with my decision.
Speaking from experience Ozzy, wanting to be put into placement should truly be a last resort. If you want some honest answers as to what life is like as a foster child I'd be happy to give you a clear picture of what exactly it is you are asking for. I also know what it's like to be in the kind of home situation as well and I definitely understand your desire to leave. While time for me now as an adult seems to fly faster every year, when you are 16 in foster care- every day is a year, and typically not a happy one. Satin's advice is a good place to start in the mean time.