I do them in the order that is recommended. If you read the back of the DVD case, it tells you what number that DVD is. I'm not at home, so I can't check my set, but I think first is arms, then legs, then chest, then back, then total body. Abs and shoulders are mixed in there, but I forget where.
Each DVD has one 20-40 min of weights on it (the first DVD has arms, the second legs, etc). And then 4 of the DVD's have a non treadmill cardio of around 30 min and then a treadmill cardio of 30 minutes.
I do the weight section as is and then I either do the non treadmill cardio or my own cardio each day. On the total body day I do not always do cardio. On the 6th day I do a 40 minute cardio. On the 7th day, I rest.
I have alternated a week of Cathe with a week of Barry. I used gym styles for my week of Cathe but broke them up into a 4 day split the way BBC is broken up. I read a post elsewhere that people have used the pure strength series.