I've been working out on and off for 5 years, for tone, and GPW's advise has helped really me at least thrice. So I recommend you listen to him.
The other thing is that there are a lot of myths when it comes to working out for -- for some reason. So get to the facts. Beware of gym rats.
At some point you should move on to free weights, because they are so much more effective, but I was on the machines for at least a year before I moved on. Form is very important, and it is difficult to fuck up form when using machines.
Here is a website I use, which has been helpful:
http://www.bodybuilding.com/fun/bbmaintrain.htmMy advise is you sign up at a gym and meet up with the trainer there, and he will plan things out for you.