Is there a free alternative to copilot that doesn't require the helpee to do anything ever
Simplest and cheapest would be to setup iChat on both computers and use Ask to Share screen feature from context menu.

Usually it will work from the start. Sometimes you need to configure router, here is a list of ports used by Apple services. Enabling uPNP or NAT-PMP on the router will usually work. In any case you need fast enough connection for it to work (at least 300kbps recommended still it's better to have faster one but what is more important is quality of the connection).