Get a job in catering. The snackier the food, the better - I would probably hae starved without making a spare couple of sandwiches for myself for 6 months when I was a sandwich maker.
Downside: Everyone in catering is a cunt.
Herbs help - a bowl of pasta becomes less than deathly depressing if you throw some basil and oil into it. They can be expensive, though. Supermarket value chips (sainsbury's used to be good for this, they may still be) are often about £1 for 3 kilos. Handy side dish and a tolerable meal if you throw some salt and pepper on. Get chatting to supermarket and corner shops taff and find out how their bargains work and when things get marked down for quick sale.
If you do the food shopping by hand and carry everything, always buy spuds. They're cheap, and heavy, and always by the door, so that you end up getting your arms knackered before you can buy anything you don't need. Plus, they're versatile - slice and fry them and sprinkle with salt and pepper (and rosemary if you have it) for a last-ditch meal. Bake them and add beans and, if available, cheese, for a filling and tasty meal.
Sausages are your friend. Don't go ultra-bottom of the barrel, but do go cheap. You can get some surprisingly tasty and un-fatty ones (that aren't necessarily all bread) for not much. Sliced and fried with onion and sage, they can go in a sandwich or in pasta, or be eaten as is. Baked with potato, bread, garlic, mushrooms and olive oil, they can be lovely.
Pasta is your friend. Rice and peas are your friends. Tinned fruit is cheap, nutritious, keeps, and can be snacked on at least at home when sugar cravings strike. Yoghurt is good value for money - add fruit and/or honey and/or cinnamon for a very nutritious treat (good for warding off colds, this). Be extremely pleasant and fairly flirtatious with checkout staff. They're bored, underappreciated and will seldom miss an opportunity to just shrug and say "don't worry about that" if the machine's dicking about when they scan your bread if you earn it. Avoid the really young ones - they'll be more likely to toe the line out of inexperience and lack of general disillusionment and hatred of their job. Don't get me wrong, weekend and part time staff are the best thing about retail, but they are often terrified of going "ah, fuck it" and often bullied by their managers and customers alike.
Buy flour. Baking is cheap and easy and you can get a lot of variety out of a few ingredients. Mashed potatoes with loads of flour and a bit of butter make potato cakes - filling and, with butter, quite nice. You can also throw any ham or spronions or mustard or cheese in, too.
Depending on where you live, you may be able to blag into conventions, business presentations and mass interviews to score free biscuits and juice. This can require a bit of research, though. Depends what's near you.
Re-use teabags - even if you like it strong - each can make one and a half cups of moderately strong tea.
Round up everything you buy to the nearest pound. Don't buy anything you don't need two of.
Browse moneysavingexpert.com - there are some excellent cheapskates on there and they've an eye for a bargain.
Visit nearby friends. Crash barbecues.
Have fun!