Bascially if you want a bone to stay still from 00:00 to 00:10 you need to have it keyed in the same place at both those times.
If your bone is moving from 00:00 to 00:20 then you can copy the keyframe from 00:00 to 00:10 to get the above effect.
note: What bones the keyframe button (and copy/paste ) operates depends on what filter (single bone, branch, whole model) is selected.