I think it is important that you enjoy what ever exercise you do otherwise it becomes a chore and you are less likely to stick to it. I do a lot of mountain biking (not to lose weight but because I enjoy it) I lost weight without even realising (didnt really need to lose the weight as I am only 12stone now). And whats more the fact that I enjoy cycling means I go to the gym to get better at it and this I enjoy rather than endure. It is important to have a target that is quantifiable (not just lose weight) such as knock 30 seconds of your time at running a mile or increase you biceps by an inch etc. Make sure your goal is challenging but achievable. Hope this is of some use Dan