Watch the String Gauges online guitar lesson by TrueFire from Play Rock Guitar 7: Style Variations
String Gauges - Overview is a video guitar lesson presented by Andy Aledort and is sourced from Slide Guitar Power.
What gauge string to use is another essential decision to make for playing slide guitar. I use .010-.046, which is probably the most popular electric guitar string gauge , meaning that it is a gauge that is used most commonly regardless of musical style on the electric guitar. I used to use very heavy string gauges for slide, .014-.056, but a gauge that heavy prevented me from using the guitar for conventional playing as well. The advantage, though, was that I could hit the guitar very hard with both hands and the guitar would stay in tune and sound great. With .010s, I can use the same guitar for slide and for conventional fretting. I believe Duane Allman and Johnny Winter used .009s back in the late '60s/early '70s whether they were playing slide or playing conventionally.