Shutoff valve leaks badly?

when a valve is left open for a long time all is well until you move the stem quit common with 2 wrenches hold the body of the valve with one and with the other tighten up the bonnet packing nut where the water is coming from just a little twist should do it 1/8 to a 1/4 turn .what this will do is smash the bonnet washer a little tighter to the valve stem shaft. gl