My family is actually pretty well off (upper middle class), but I have never been one to buy much of anything (I have my weaknesses though
). Instead of buying fruits which are frequently expensive and can go bad easily, I generally buy fruit juice. At about a dollar per 1L box, I spend almost nothing on getting part of my fruit and veggie intake for the day/week/month. I still like drinking, which gets very expensive if you do it improperly, so I generally end up drinking at my place or someone else's for a while before going out. Once out, nurse the drink or two that you buy for the night. I've saved upwards of $50 per night (on the weekend) doing things this way. Turning off lights when not in use (I mean consistently turning them off throughout the day and night) both lowers the electricity bill and is better for the environment. Same goes for keeping the heat low (18-20 degrees celcius at a maximum) and just wearing more clothes or a blanket instead of pumping the heat up. I don't like shirts with logos. To augment my collection of solid t-shirts, I recently discovered t-shirts in bags (in the underwear section no less) by companies such as Fruit of the Loom, at $8 for two t-shirts, and they fit nicely as well! Finally, when I grocery shop, I decide to buy something based on price per serving (approx meal size). I try to keep it below 1.50 per meal (not including milk and juice), and it works pretty well with most things. Just know how much you eat, the portions of what you're buying, and do a little quick math. I spend about 15-20 dollars a week on groceries, and have a decently varied diet.
Prices are all in CAD so I'm sure it's even cheaper in the US.