Leaving the glow-starter on the plug for about 10 seconds before you try to start the engine will make it much easier to start than if you tried to start the engine immediately after placing the starter on the plug. Although the engine will not become noticeably warmer, the temperature in the combustion chamber will increase. A warmer combustion chamber = easier starting. It may just give the chamber the few extra degrees to allow it to start.

If trying to start an engine in cold weather, the previously mentioned methods of engine warming work perfectly.