Stobe your subject

Not to sound insulting, but I have to ask. Are you using this in TTL mode on a Canon camera, or in manual mode (on another brand camera)?

If manual, I usually just chimp. Start with the flash on 1/16 power or so and just turn it up/down to taste. For me though I want the flash to add just a little fill light and not be the primary source. So what is it that you are trying to do with the flash? TTL on camera? Manual off camera? Fill light? Primary source?