Rotating your tyres - things to be aware of.

It's common wisdom that rotating your tyres is A Good Thing. It helps even out wear especially on front-wheel-drive or rear-wheel-drive where one pair of tyres will typically wear quicker. There's a couple of things you need to be aware of when having a tyre rotation done though. Unidirectional tyres must be kept on the same side of the car - typically the front and rear lefts will be swapped, and the front and rear rights will be swapped.
If you don't have unidirectional tyres, then front-left to back-right and vice versa is just fine.
But there's a slight wrinkle in the scheme with a lot of modern cars : TPMS. For the average family car, the TPMS system (the tyre pressure monitors built into each wheel) is a single-point-of-failure system, meaning that if any one sensor registers low pressure, the car will present a single warning light on the dash and it's up to you to find the tyre in question. For higher end vehicles though - Range Rovers, BMWs, Mercedes and the like - they sometimes have TPMS that will tell you which tyre needs attention. This makes tyre rotation more complicated because you either have to take the tyres of the rims to ensure each rim and sensor stays on the correct corner of the car. Or you need to have the car re-learn the location of each sensor afterwards. Generally speaking this isn't easy to do - it normally requires access to the computer via the OBD-II port and access to someone who knows that they're doing.
There is one manufacturer - and I can't remember who it is - who made this easy though. They have a mode where you, as the owner, can put the TPMS into 'learn' mode and then it shows you on the dash which sensor it wants to learn, in order. To 'teach' it which sensor is where, you bleed a little air out of the tyre. So when the car indicates "left front", you go and blip a little air out of the left front tyre, and it then associates that sensor (the one that changed) with the front left corner.
Anyway - the point is this - by all means rotate your tyres, but be aware of the little pitfalls when it comes to tread directionality and TPMS.