need help setting up exercise schedule

KAK68

I like to walk, elliptical,wii exercises including biggest loser, step master and have done Richard Simmons video's Sweating to the Oldies. I have been walking or doing elliptical for 40-45 mins a day at least 4 days a week. I know you need to mix things up so just need some advice on how to do this- do i stick to one activity one week then do another the next week or mix them up during that one week? I am also trying to fit in some bowflex time for the arms and stomach. Any suggestions would be appreciated.