So you want to get fit! Presumably you also want to keep fit too? At its simplest, your idea is brilliant! In the cold light of day though - you will need to be motivated to get fit and when it comes to the keep fit - well ona cold winter's night you will know what we are talking about.
Whether your stated goal is to lose weight, build muscle, or train for a specific sport or event, the heart of what you will be doing is to get fit. So what exactly what we mean by getting fit?
There are a number of different ways of measuring it. If you are looking at body composition, then getting fit will entail changing the ratio of muscle to fat in your body - more specifically gaining muscle, and losing fat. People measure this in a number of different ways.
Some simply use the scales, although this can be an unreliable measure, as an increase in muscle weight can offset the loss of fat. Unless you are going to pay money to have somebody test your body fat percentage, the two best ways are probably noticing the changes in the tightness of your clothes, and taking an honest look at yourself in the mirror from time to time - naked of course.
If you pay any attention at all your workouts, then you will certainly notice a difference there. If you are doing resistance training, you will find that you can lift more weight for a high number of repetitions, with less difficulty.
On the cardiovascular machines - for example the treadmill, the rower, the stepper - you will find that you can work longer, at a higher intensity, with less feeling of exhaustion. If after working out for a few weeks you find that none of the above is happening, then it would be well worth consulting a trainer, in order to ensure that your workouts are appropriate for the goals that you have in mind.