I want to make a 3 or 4-tiered stacked wedding cake. I need to know two things :
1) what size round look the best stacked and
2) how high should I make each stack

Thanks

It definitely depends on how many servings you need. You can do a 2", 3" or 4" difference between the tiers & they all look nice. For a wedding cake I like to have 4 layers of cake & 3 layers of filling so they're pretty tall (maybe 5"?)
HTH

I usually make each tier, 2 layers/ filling - about 4". As for sizes it depends on the number of people you need to feed. Take a look at the wilton site, it may help.

http://www.wilton.com/cakes/tiered-cakes/serving-amounts-all.cfm

Each "stack" tier shoud be at least 4" tall. Two 2" layer cakes with filling.
Like everyone else has said it depends on how many servings are going to be needed to determine what size each tier should be. The blue and white cake in my photos is a 10/8/6 inch and feeds about 54 people just to give you an idea.