The basic philosophy. Learn anatomy! Or at least Anatomical shapes. Knowing a bit about structure and musculature helps to knit a character together. Even if that character is a bunch of tubes and boxes, tying them together in a natural way can reside in that knowledge.
In working out a character, collect your research and if you're working on an exact pose from photo or art: Size It To The Figure You're Going To Sculpt! That is, Print out the size of the sculpture you want to make and print it on cardstock. There is NO more valuable tool than a cut close picture, that you can place directly behind your sculpture as you work on it. If you look at Jenny001.jpg in my gallery, you can see that I've worked out the armature WITHIN the art. This is even more useful if you are trying to duplicate the actual pose in the art. Since I am creating an original pose from the static figure, I use it only in measuring out the length of body and limbs. However I'm also using about 4 more pieces of art that are printed out to the size of the sculpt for reference, and often hold them right behind the sculpt to gauge the measurements.
Work out a basic structure over the armature! Detail comes later. As you go along you will start to rough out detail, but assume that it is a temporary thing. The main goal is to get a natural body structure and pose. Even before clothing the body MAKES the clothing work. In the case of Jenny the robot, who has a metal body, I've worked out several rough details. What you don't see is the number of times I've eradicated that detail to change the body structure again so that the detail looks "right" on it. So structure comes first, pose second, and FINAL detail comes last.
Last, don't be afraid to rework the pose. If it doesn't look right, you have to be willing to go in and wrench a body part into a different position or take a pair of needle nose and move the armature around in the clay so that its not so close to a surface [which often happens at joints]. I had to remove Jenny's arms armature 2 times to reposition them below her neck properly. This cost me more than half a day, but now the body measures out properly and I can get the correct pose. When you try to sculpt around a problem, you always come back TO that problem.
All of the tools I use are in my scraps for those interested and I hope this helps budding sculptors out a bit.