Be very carefull to not get knocked off the stage because even though you might make it back, Marth's recovery is very slow and your teammate will be getting destroyed. You'll also have a difficult time saving your partner so don't even bother. Instead just focus on messing up your opponent's edgeguarding. Throw your opponents as fast as you can unless your holding them for your teammate. If you want to combo them out of the throw you have to do it before their partner can help. A great thing to do in this match is seperate your opponents so it can turn into 2 seperate 1 on 1 situations and, as soon as you get your guy of, a 2 on 1 against the other opponent. Marth's great edgeguarding means that if your partner knocks them off you should be able to keep them from getting back. Get your partner to cover you back and take care of the edgeguarding for the match.