The key for me is LOOKING. So many times I go to the supermarket and pick up the same thing without even looking at other stuff. If I actually look what's on offer I get those things Instead so it's cheaper and my diet has a lot more variety so I don't get bored x
I completely agree you definitely get in to a way of habit, my mum buys the brands and foods that my granny bought and until very recently I stuck religiously to those brands.
Buying Supermarkets own products is definitely the way forward and even doing simple comparisons, the other day I lifted a packet of wholemeal pasta without really thinking, then ended up back down the same aisle a few minutes later as I'd forgotten something-looked at the pastas again and found 2 other packets that were the same size but cheaper than the one I had.