It's certainly got harder in the last few months.
BOGOFs can be a pain., especially fruit. Do you really need 2 big bags of oranges. Half the seocnd bag usually goes bad before you've had a chance to eat them.
Every week we buy 4 bottles of Coke. Sometimes it's cheaper to be the shrinkwrapped packs of 4 and sometimes it's cheaper by by them individually. You need to check the prices.
Often frozen food is cheaper then fresh. Just compare the price of pizza!
Rob's right about Iceland, they have a lot of stunning offers.
Use own brands where possible. There can be £1 difference between supermarkets own cooking sauces and well known brands.
Check out the value ranges. Some items such as tinned tomatoes or peas are only maybe 7 or 8p a tin and taste OK. Some other items may not be as good.