One of the main things getting into a routine.
You can probably find programs to follow online and the key thing to try to stay consistent in your workouts. ie maintaining how often you workout and the intensity. Also figure out what motions works out what muscles in your body.
With the equipment that you have you should be able to hit every body part.
I think the old standard is doing 4 sets of 10 repetitions for each exercise and you can change it up a little bit. ie depending on your strength and fitness, you might want to do 25 reps if it's light weight or bands.
You can find programs online and on youtube so won't go into too much details. I think if you do a search for resistance band workout you should be able to find something. And some of those motions for resistance bands are similar to the weight machine. So you can change it up once in a while. ie sometimes do the pressing motion with the resistance band, but change it up with the bench press on the weight machine.
And make sure to work cardio in there as well.
Also there was a thread on here about pushups not too long ago:
http://www.dcurbanmom.com/jforum/posts/list/457083.page