If you are looking to get fitter, leaner, stronger and feel good about yourself then great! You're among a very high percentage of people with common goals
When you consider 'just' wanting to get fitter, stronger, leaner and better (noble goals by the way!), have a little think about how important everything is. Don't think of isolated goals or things.
We don't want to live now (or grow old) without relative freedom in our body. Freedom achieved by being fit [heart + lungs], strong [useful to move things around and move ourselves], mobile [injury resistant, able to express ourselves in any direction] and pain free [a touchy subject, but basically having our physical social and emotional needs met]
Most people are training for immediate needs, short term change, medium term lifestyle and long term health. Methods can change, but I don't think the principle of what you are looking for does
So choose something you enjoy firstly - so that you've something to look forward to
Choose something effective at getting you what you want
Choose a safe, supportive, welcoming, nurturing environment
Choose experienced and personable teachers