The main speed technique is rapid-shooting. If you are moving while inflating enemies, you will be able to explode them much faster.

Most items probably aren't worth going for in speedruns, except for the ones that make you go faster (look for the shoe-with-wings symbol and the lightning symbol).

If anyone else has thoughts, they are welcome to share in the forums. I doubt this game is going to get many players, but even one or two people running the game and helping find new techniques would be cool. :-)