Agree with Fuji. Outside controlled airspace nobody *wants* to talk to *you*. *You* might want to talk to somebody who can give you information/service what *you* need.
If you don't need anything you can just turn the radio off and enjoy the flight. (*) If you want information such as the QNH, a warning about pop-up NOTAMs and such, ask for a Basic Service. If you want information about other traffic, ask for a Traffic Service.
If you are on a formal flight plan and you need to divert, make sure you tell some ATC service so that they can inform your destination you're not going there anymore, and (if necessary) your diversion airport that you're coming. If you're not on a formal flight plan it's just like being late or absent for dinner at home: Make sure you inform the people that may be expecting you of your changed plans.
That's all there is. The controllers work for you and the radio is the way you can get them to work for you. Don't need them? Don't talk to them.
Of course inside controlled airspace this is totally different. You have to talk to them and follow their orders.
(*) Legally you have every right to turn the radio off. However that is considered by most to be bad practice. It's usually better to tune the radio to whoever provides the FIS or LARS service for the bit of airspace you're flying in, and monitor that frequency without actually speaking to them. You might pick up information such as a QNH change that way. And if somebody wants to talk to you, for instance because you are about to stray in controlled airspace, the controllers stand a fighting chance of actually getting hold of you. And you've heard of the listening squawks, have you?
Last edited by BackPacker; 19th September 2012 at 21:34.