Ways to wake computer when someone want to play on server!

Hello, I want to run a server at home on a PC, but don't want to spend money on electricity. so i was thinking i could make my computer WakeOnLan when someone wants to get to it. i don't know how to do this and would appreciate help. Also when i put my computer to sleep and then turn it back on i get the overloaded message.

I don't want this answer: "Just keep it running all the time" or "never put it in sleep"!
Also I know my computer will turn on every time someone refreshes there server list because I want my server to be able to look like it is on!