Spanx?  Something else?  Tell us about the "foundation garments" you will wear to make sure you look sleek beneath your gown. 

Well, my crinny is a sucker inner, lol!! So much more than that I am unsure, poss a pair of spanx so I don't get thigh rub

Me?  I'm going for major architecture under there!  A long-line bra, Spanx, and a crinoline with a sucker inner waist.  The crinoline also helps by making it look like what poofs out below the waistline is just the crinoline, not me.  ;-)

I think I want a bustier/corset. I've never had one, and think they are sexay, and it's dual purpose - won't have to worry about changing ;)

I did the bike shorts type spanxs. 

I'm doing a long-line bra and spanx-- the ones that go from your knees to right under your (normal) bra line...  But now I'm curious about this crinoline that sucks you in.. where did you ladies find that?!

My dress had some boning on the bodice and fit me really well so I ended up not having to wear anything under it - it smoothed all the bumps down nicely on its own!!

I guess it all depends on the type of dress material but it's either a long-line bra or a corset.  I have spanx and I just do not like how the top part rolls down.

I have it picked out, just need to order it:

This longline bra

And not sure what else. I'm likely just wearing a flowy empire dress so not much would be needed below the waist...

But I love that bra simply because it comes in a 48FF which is my size, though the band size is one size bigger. The reviews I've seen on it reccommend ordering one band size up. :)

afowler8, my sucker-inner crinoline is a David's Bridal Style 603.  They describe it as having a "Power Net Waist."  I got mine used from another bride via eBay.