Valve Stem

Dont tighten the valve stem up to the rim instead lock the valve nut against the valve cap which is in the opposite direction to the rim. This makes sure your cap doesn't come off but it also releases the pressure on the valve stem and allows it to move, this in turn reduces the likelyhood of the valve stem ripping of the tube.

Believe it or not valve stems getting ripped off the innner tube happens a lot, especially where the tyres are not sufficiently locked to the wheels. Also try to get metal valve caps that double up as a valve remover tool, always handy when suspect leaky valves are in queation.