Watch the Tunings online guitar lesson by Angus Clark from Hard Rock Survival Guide: Rhythm
I will be demonstrating everything on a standard tuned guitar or standard with drop D. This is not really representative of what is currently happening in the industry, because a large number of the more successful bands in hard rock from the 90's through the 2010's like Breaking Benjamin, Crossfade, Five Finger Death Punch, The Sword, etc. are taking a page out of Sabbath's book and tuning the whole guitar down anywhere from a minor third (C#) to a fourth (B) with the corresponding "drop whatever" (C# with a drop B, C with a drop Bb, etc.). The shapes and so forth are all the same as in these demonstrations, but there are some issues that you will need to address if you decide to tune down. Get the right string gauge (I use .012 - .054 for a C# standard guitar) and you might have to get your guitar modified (nut width and height, bridge notches) and adjusted (truss rod, etc.). You definitely need a separate guitar or guitars to handle this kind of duty. And you need to practice on them because it actually requires kind of a light touch and pick attack to keep a guitar in that kind of tuning from sliding out of tune. To explain the tunings concisely: Standard indicates that the strings are in the standard relationship to each other. 4th, 4th, 4th, Maj 3rd, 4th. Drop means that the sixth string is a whole step lower than it would be in standard. So Eb standard means you tune each string down a half step. Eb drop C# would be the whole guitar tuned down a half step and then the sixth string tuned down another whole step further. Sabbath used C# standard a lot. Five Finger Death Punch tune to B standard. Breaking Benjamin are in C drop Bb, the Sword are in C standard, just as some examples. The entire Jailbreak record is done on Eb tuned guitars. Van Halen used Eb tuning, and sometimes with drop tuning. I mean, even Hendrix tuned down to Eb, so this is nothing odd, or new, it's how the pros get the job done.