well everyone has their own style as to drawing a body, some people create a skeleton stick figure, and draw the body from that skeleton and tweak tweak tweak till its good, some people just outright draw the body and head, then add the legs and arms later, but its when you start shading it and coloring it that you can give the body definition, highlights, etc..I guess what I would suggest for you to practice, is to find other pixelart that is similar to the effect your trying for and see how they did it, and try and learn from it.
ok, just make a circle about the size of the head and copy it 7 times end to end vertically so you've got a line of 7 circles going vertically. put these beside the head and you've got your self a guide for where the body parts should go.
heres one i did for a thread on the old pixelation a long, long while ago.
this represents the average proportions of an adult male. use the heads on the right of the picture as a guide.
shoulders are around 1.5 heads down from the top of the head, and are about 2 heads wide. belly button and elbows are about 3 heads down. hips are about 3.5 heads down, and are normally drawn about 1.5 heads wide, but i just use 1 head length for the width. knees are 5 head lengths down and feet are 7 heads down.