The valves are made so you can tighten the brass caps to keep pressure on the seals. they are only bad if you can't turn the handles, or if they turn but don't close all of the way. Tightening up the caps should cure the dripping. If not, then the seals are most likely damaged. You can replace the seals in most valves by unscrewing these caps until the handle and cap can be pulled out of the valve body. Locate the right seals, and put them back together. When the caps are tight enough to not leak and you can feel a little resistance when you try to turn the handle, they are perfect.
Rich the Viking