As you've learned, it's best to pick a main activity that you will make the center of your workout schedule. Most people create a weekly workout schedule, so get out your calendar.

Let's say you take three walks a week with a friend in your neighborhood and you know that those walks provide good cardio training. You realize that you need to add some strength training, so you decide to buy some dumbbells and an exercise DVD to use in your home twice a week. Now you want to add a little flexibility to your program, but you're running out of time between your job and your family. You decide that, in this case, all you can manage is some stretching in front of the TV in the evenings.

That's fine, by the way. Cross-training doesn't have to be intense. However, you might want to invest in a stretching DVD (they are usually fairly short) to give you some ideas on what to do.

However, let's say you are someone who likes a lot of different activities, such as walking, swimming, weight training, yoga, and Pilates. How can you fit them all in? Chances are, you can't, not in one week anyway. If that's the case, think about the benefits and time costs of each activity, and try to be sure you are doing two different types of activities on consecutive days. For example, don't swim on Monday, dance on Tuesday, and walk on Wednesday. Stick some weight training in between all of those cardio activities.