I work out at a gym, Monday through Friday ... typically for 60-70 minutes.
The first part is weight training, which involves a rotation of several routines. I pick a different routine each day ... typically with 5 to 7 different stations, each targeting different muscles. I'll work through a cycle of doing a set at each station, then repeat the cycle two or three times, depending on how many stations I'm working at on that given day. I always end my cycle with a "core" set ... something like crunches, or sit-ups on an inclined bench while holding a 10-lb medicine ball ... something that focuses on abdominal strength.
The second part of the workout is cardio ... depending on the machine it'll be between 30 and 45 minutes. Elliptical and bicycle get the longest sets ... treadmill and stairmaster get the shortest because they're more intensive.
I found that the key to sticking with it is two-fold ... first, get into a routine and don't allow yourself to find reasons to break the routine. I'm at the gym every weekday morning at 5 AM, when it opens. I have workout partners who meet me there, and we work out together. Second is set short-term goals for yourself, and work toward meeting them. Choose achievable goals, and once met, set another goal.
Personally, I found that working out doesn't really do much to remove weight ... and working out makes me hungry. So after a few months, I decided not to make my goals about body weight, but about performance ... such as reaching a particular weight on a machine ... or being able to perform a certain number of reps at a given weight ... something that makes me push myself. On the cardio systems, it's about being able to maintain a given resistance level for a specified period of time. Those kind of goals help you take it seriously enough to not get complacent ... but you also need to be careful not to get too aggressive and hurt yourself. For the first year, I hired a trainer I could work with once a week to help me develop my workout routine. It was well worth the investment.
You can also establish long-term goals. For example, I'll be 59 on Sunday ... my current long-term goal is to be in better shape at 60 than I am at 59. Having that goal will make it easier to keep me motivated to get into the gym day in and day out ...
... Bob (Grateful Diver)