General tips
Buy Local Food : See if you can find out where your food has gone before it gets to your plate. You may be suprised by the results. Often it will make financial sense for companies to transport food enourmous distances by planes, boats and lorries. This dosn't take the environmental cost into account (which of course is likely to lead to greatly increased economic costs in the long term).
Making your own lunch instead of buying from a sandwich shop saves on packaging, and could also save you approx £4 a day or £1,000 per year!
Oven Tips : With conventional ovens, minimize the preheating time. Unless you're baking breads or pastries, you may not even need to preheat.