is the distance from the flange to the nut the same on the drive and non-drive sides? (do you have to dish the wheel when lacing it?) Also does the difference in flange sizes make a difference?

with a BMX hub the distance is pretty equal. any slight difference is usually not enough to require different length spokes, but may need some slight dishing.

different flange sizes:

36 hole 4-cross will be all the same size spokes, regardless.

any other hole count and/or lacing pattern will require different length spokes on each side.

I gather your reffering to profile mini or the likes with diff flanges, I've heard bout 2-4mm longer is about what you need on the lower flange, but a lot get away with just doing it the same. I'd advise going 2mm but talk to someone who does then more often, like that bloke from empire blanking his name but somebody here should know.

Tom @ Empire is the man when it comes to things that roll.He builds wheels non-stop and has probably encountered avery hub/rim combo.............512 474-4BMX is the digits.

It depends on the brand of hub. But I'd say most new school cassette hubs will need to have an offset, because of the amount room the cassette takes up on the drive side. ITS ALL ABOUT GETTING THE HUB CENTRED. Get a good spoke calculator off the net. Some Excel Spreadsheet ones will have a hub and rim data base built in. The spoke calc will then work out the offset and spoke length. For a strong set of wheels go 4 cross, if your chasing lightweight go 3 cross and possibly radial lace on the front, pending what your doing with them.

PARK make a dish/offset tool that will find the centre for you once you tension the spokes. This is measured from the face of the rim(THE BRAKING SURFACE) to the cone lock nut on each side of the hub. Especially these days with MTB's and disc brakes. The wheels must be centre of the forks and the rear chain stays, Anyway, it's a really simple tool, and well worth the investment if you want to build a good set wheels.