Heavy Rock bands use lowered tunings because they produce thicker and heavier guitar sounds. They place the guitar pitch somewhere in between a standard guitar tuning and a bass guitar tuning. The thundering low, growling rhythms sometimes have limitations. Not all solos sound great at the lower pitch and sometimes there is so much slack on the strings, chords lose their distinct quality and sound mushy.

SLACK TUNINGS
1. Use heavier strings for the lower tunings like C# and B. Try .010s or .011s, maybe even .012s. The higher tension strings will help you stay in tune and avoid intonation problems. Using light or extra light strings(.009or.008s) when playing in B or C tuning creates slap noises and flap onto the frets.
2. Press the strings lightly, as strings will be far easier to bend in and out of tune.
For DROPPED D TUNING/
Tune your sixth string down one whole step (the distance of two frets or two half steps on your guitar) to low D. The rest of your guitar strings stay in standard tuning-first to fifth strings(E-B-G-D-A).

For D TUNING/
Tune your guitar down one whole step on each string, low to high:D-G-C-F-A-D.
For C TUNING/ Tune your strings down a minor third.
For B TUNING/ Tune your strings down a perfect fourth if your guitar will let you. At this point were talking some real guitar growls!
Hear more from John Tapella at http://www.guitarempire.com