When I try to add my own skins in, the skins come out glitched.It's like it has no head, part of their body is missing.Pls Help or tell me what to do

Are you sure you are:

1. Naming the skin files correctly.
2. Using the Steve skins, not the Alex Skins
3. Restarting the Game after you have inputed a new skin, or set of skins?