First tip for every person out there who needs to live frugally is make a list. A list can save you time and you can work out beforehand how much you can spend and make sure you stay with the list.
Secondly where you shop. Believe me this makes a difference especially in South Africa. Even in places like UK I could notice the difference in prices from a shop in central London to one in the outskirts. South Africa it is easy to spot where you would be able to find cheap groceries. Shoprite is the best super market for budget shopping you just have to have your timing right. Early on Thursday mornings they usually stock up for the weekend traffic and it's also the shops most quiet time. I know it is odd to stress when you go shopping but in South Africa you can never be to carefull and if you are white you would stand out like a sore thumb at the local bargain shops on a Saturday.
Timing is also crucial to find bargains. Rather do your shopping at the end of the month, put away your monthly allowance for food for then, the shops tend to have more specials and you won't have to fight to find good cheap meat.
Stay away from fast food. Rather buy everything you would like on a burger and make it yourself. Not only would you save on expenses it would also be much cheaper. And remember if you do it right it won't take so long to make. Once in a while I'll buy a back of skinless chicken breast, which is really not that expensive if you buy at the right place, a couple of buns, lettuce and mayo. The chicken does not even take 10 minutes to make, while it grills I would usually prepare the buns with the mayo and lettuce and viola chicken burgers. It's not the deep fried variety of KFC but believe me it's much better. What I would normally pay for one burger there I can make 4 burgers at home.
Buy in bulk, the price these days tend to rise pretty quickly. For example a pack of diapers cost R130 at checkers but it cost R80 at Christmas time. That was like 6 months ago. Plus most stores has buy two get one free promotions.
Using coupons are nothing to be ashamed about. If you can get them use it. Even those shopper cards that you can get at most stores if you can get savings and even more promotions and so on.
Here is a tip you might not expect but watch the items till up on screen and double check your slip with your items afterwords. You would be surprised how many mistakes can happen sometimes wrong labels or even an item scanned twice it happens.
If it is possible buy fresh produce from local markets. They need to be sold of quickly and you can sometimes barter with the price. They are also less expensive because they do not have all the packaging supermarkets have and all the overheads of larger businesses. In London there was a fresh vegetable stall right by my bus stop so I used to buy all my veggies there. In South Africa they are a bit harder to find they are more available in the summer months. I know you can go to Epping industrial in Cape Town there are many markets with lots of competitors so the prices can be bartered down, if you want to of course.
The main thing to remember is to set yourself a limit and stick to it.