Well its all pretty common sense stuff really. But here is the basic set of tips to keep in mind. Now note some of this make a big difference and others not alot.
Check Tyre Pressure (upto 3% difference)
Get rid of clutter out the car to reduce weight (upto 2% Difference)
Turn of the aircon (upto 8% difference)
Dont run the car on a full tank (upto 1% difference)
Always keep in the correct gear
Slow down naturally without the breaks where safe to do so
Turn of the car if your going to be stationary for more than 30 seconds
In vehicles built after the mid 1990's when you take your foot off the accelerator peddle the fuel is cut off to the engine. So this means as you approach a round about come off the fuel earlier and coast in gear up to the round about the brake if you have to or just carry on you will use a lot less over time doing this. I have a 7 seater 1.9 diesel Renault scinic (130 bhp) and keep 40psi in the tyres and drive like this and get 55 MPG around town and 84 MPG out of town. If you do it right you don't get in the way of people aswell this is driving at speed limits too. Try it.
I bought some Michelin energy saver tyres for my Toyota Corrola 1.6 petrol. I have now done about 30,000 miles and it has improve my MPG buy 5-10 miles per tank. They are about ready to be replaced now though.