I like group work. I usually take control as the natural leader, and manage to pace our assignments quite well. I've also been lucky to have great members in my group most of the time, but even when I had naturaly non-motivated ones, it's not that difficult to motivate them if you figure out how they like doing work. For marketing, especially, it's great to break the project into smaller parts, and then make it more practical for everyone. Deadlines each week will make everyone also work harder, and group members will be less likely to let the fellow group members down.
If you have a weak link in the group, it is also important to acknowledge that and either ask them about the problems they're having, and help them with it, or reduce their workload (it's better for you to have more work, than have something crap submitted at the end of the semester).
In later year subjects, you can tell the rest of your group that "this is it. lots of us are graduating, so this is our shot at getting a fantastic graduate position, by getting a great mark on this assignment". Also, make it clear what you want to get: I usually tell my group that I'm aiming for an HD overall, and want to get them the same mark.
Try and become friends with your group members. Again, it's difficult to let down your friends. Although, it's more difficult to be stern with them if you become too close. I met a bloke in first year econometrics class, and we became good mates. We then took an advertising subject together and were in the same group. Luckily he was quite productive and great, but if he wasn't it would be difficult to say anything and put the friendship on the line. I'll be doing another group project with him this semester in services marketing.
Don't sit next to asians if you don't want to be stuck with a fob. I know it sounds harsh, but most international students here are Asian (especially at USYD/UNSW/UTS), sitting next to caucasians will reduce that risk (although you may still get a European student).
A lot of the problems could have been avoided. Don't leave everything until the last minute - everyone should have sent their work in at least 5 days before the assignment was due.
Have set roles for everyone, for example, in marketing:
-Team Leader (who also doubles as something else)
-Marketing Communications Manager
-Market analyst (including competitors)
-Editor (best if it's the team leader)