Tutorial by Galen Maly aka Yume

Required Downloads
Avisynth 2.5.x
MeGUI (requires Microsoft .NET Runtime 2.0)
sample avisynth script - test.avs

Suggested Downloads
Lagarith Lossless Codec

FAQ

Q: What's the deal with the slow/slower/slowest profiles?
A: Basically, slowest means highest quality. If it's going too slowly for you, you can try the slower and slow options.

Q:Do I really have to edit these avisynth scripts?
A: I have yet to find a simpler way to encode h.264 without the avisynth scripts. As soon as I find a way I will update this guide..