Hey fellas,

No newbie to guitar or the blues here...been playing five years or so, but just venturing into the realm of blues slide guitar right now.  My question is, say I've got a twelve-bar in D, is there a certain slide tuning that's going to sound better over that shuffle?  Or is it more trial and error.

I'd say open D (DADF#AD) would be an obvious choice but open G (DGDGBD) should also work. Anything that gives you easy access to as many notes in a blues scale or a mixolydian mode would probably be preferred. But it really depends on whether or not you want you just want to solo or also be able to play some chords and follow the progression. The only other obvious choice would be DADGAD sort of giving you the best of open D and open G. But really it shouldn't matter, it's got to come down to trial and error. Find a tuning that works for you in another key and just transpose what you can. If you're daring you could always just tune all you're strings down a whole tone and pretend you're playing in E, a key any experienced bluesist should know cold. Happy sliding.