The more muscle you can build, the more calories you will burn, even while at rest. The main thing I tell my buddies is to watch the carbs, especially after lunchtime. Cardio is something you can't skip either. I'd say a good 20-30 minutes a day if you go to the gym daily. Try to use moderately heavy weights, say some that you can do 12 reps of 1st set, then add 5lbs or so for 10, then another 5 for 8reps. I went from 6'0 and 150lbs with a max bench of ~175 up to 185lbs and a 380lb bench. I have a pretty high metabolism so I can eat pretty much whatever and it doesn't hurt me, but I only have about one cheat meal a week for a reward.
Basically you are what you eat, so if you eat junk, that's what you'll be. Your body will try to hold onto its fat reserves for as long as possible, so you have to keep pushing your body further so that it has to release some of it for fuel.
Also, if you decide to get a personal trainer to help you get started, make sure they practice what they preach. If they're not in good shape, by that I mean they atleast look like they use some of the equipment there regularly, then find somebody who is. From what I've seen, the guys who know what to do and actually do it will be of more help than the ones who only try to instruct you.