Here are just a few, some have been mentioned already for sure.
Get a check account, a savings account and keep your access / credit card. Make arrangements that you cannot access the savings account unless you go into the bank, or at least not from check-outs in markets. Have your pay put into the check account, then have the bank transfer a specific amount every months or two weeks, whatever they will into the savings account. Make sure they do not charge a large fee to do this. If they do, then make the transfer yourself.
People talk about turning off lights. Well that's true, but the real users of electricity (or gas) are heating appliances like kettles, washing machines and driers.
Leaving a clothes iron on for an hour used as much power as six or ten light bulbs of the old kind. If you are going to iron clothes, turn on the iron and do several items, the iron uses most power when it is warming up. Use a clothes line instead of a drier. I'll bet your grandmother got on OK without a drier. If you have to wash, the weather is wet and cold but you don't need the clothes for a few days, hang them on a line in a garage. They will be close to dry after a day and if you do need them a short spell in the drier will set them up.
Another thing that bleeds electricity is stand-by settings on TVs and such. Pull the plugs from the sockets or switch off at the power socket. Some of these use as much power as a light bulb when on standby.
The most expensive form of electricity is batteries. If you have a radio or other item that is AC/DC run it on mains power.
Some people say buy this or that and you will save money. I'm pretty doubtful about some of that. Making your own things can be cheaper, but you really have to consider whether you can do it and how much the tools or materials cost to start with. One lady gave up on knitting when she calculated she could buy good sweaters for less than the price of the wool she needed.
Think about what you buy in the supermarkets. Many premium price goods are placed at eye level where people are more likely to grab them. The cheaper lines, which are often just as good are on the bottom shelf. if you like a particular brand that is a little more expensive then by all means go for it but if you are buying hand soap then the cheaper bars are good and sometimes better.
Buying a major appliance? One thing that I noticed in many consumer reviews of these from stereo to refrigerator is that the really cheap ones are not often very good, the medium price ones are very good and the really expensive ones are not much better than the medium price. Look for the models in the middle of the price range and you probably won't go wrong. A lot of features look fine, but they don't add to the quality, they might even detract from it, and you probably will not use more than two or three of them.
That goes for clothes and shoes as well. Fashion. Well it is best to take the fashion magazines and recycle them. They exist to make you want to buy some product that is only made to be bought. The best dressed woman I know is a French lady and she does it on the KISS principle (keep it simple, stupid). She never wears stuff with logos on it either.
Stop buying cosmetics. Most of them are the same stuff in different bottles with different perfumes and dyes. One lot of skin cream for face and hands is all you need. (I happen to know something about these, having worked in a related area for a while) Shampoos and conditioners. Did you know that conditioners are made up of much the same things as shampoos but in different proportions? Try washing hair with only conditioner and see what you think. The result will depend a bit on the quality of the water whre you live.
Take fruit to work. Cheaper than bought stuff and better for you.