Basic design is pretty simple. Runner length/width and plenum size are the big factors. You want the most velocity and volume. Too much volume will decrease velocity though. There are also a bunch of little things that effect on how good and evenly you distribute air like thermal mentioned. You wont know this unless you go back and forth from a flow bench to a dyno and make a couple of IM to understand what best suits your engine. In other words, spending a lot of money.

This all depends on how well you designed your cylinder head and where you want your power band. If you have a stock or unfinished head then I wouldn't recommend it till you have run out of things to do.