I tend to pick for different reasons each time I play. Last time through I wanted to be able to make use of every item in the game so I went with F, Th, WM, BM.

The time before I went with the NES default party just to try it out -- knowing where I was going certainly helped make it easier to play and I had a lot of fun with it.

I guess I would say that in general I do aim for versatility in my party combination which means a Fighter and at least a decent degree of healing and buffing as well as elemental damage.