Setting Proper Air/Fuel Ratio.

Hi guys, been doing a bit of research online on how to set up my carburetor for the best air fuel ratio on my Suzuki. I recently got it working after a while but I think it is running a little too rich at the moment. I found online people talking about checking the spark plug condition to figure out if its too rich or lean as well as a company in the UK called gunson which sells a neat little see through sparkplug so you can colour tune your bike. Unfortunately it seems the gunson spark plug is sold out everywhere in 12mm version. Just wondering if anyone had any other tips or ideas that I could set the bike up to run a little better. I cant seem to find any factory settings for my bike either which isn't helping the cause. Thanks!