Petrol driven equipment - do's n don'ts

I need some advice on petrol equipment: strimmers, tillers, lawn mowers etc.

I need to understand the best way of managing the fuel on these things.

 I have a Ryobi strimmer (2- stroke, 2 years old) and a Mantis tiller (4 stroke, bought this year and I love it).

Now obviously I dont use these things every day of the week so there is a lot of fuel sitting around in the petrol reservoir and in my fuel can in the garage.

 I read that petrol deteriorates and can cause problems to the carbs/ spark plugs (which is probablywhy the strimmer wont start at the mo) so how do others manage their fuel to keep the equipment running.

Any advice will be appreciated.

Like flatcat says, Pour the fuel out of the fuel tank back into the fuel can. I then start the machine on what is left in the machine. It runs for a second or two then stops. I then know there is no more fuel in the equipment.
You can get an additive to put in fresh petrol that will keep it in good condition for a year. Briggs and stratton sell one that they recommend for use with their engines. It isn't expensive (compared to a strip down at the workshop) And I can't recommend it enough.