It's generally simple. Just make your image sizes a multiple of 16. So if you want to make a 32x pack, then make all of your textures bigger by a multiple of 2. So blocks and items would be 32x32 pixels and the player skin would be 128x64. You'll need MCpatcher or Optifine to be able to use higher resolutions, though.
"Every time a bat gets killed, a miner falls in a pit of lava while carrying half a stack of diamonds."