As a general rule :

• Never doing stuff that will take care of itself. Since the dishes want to dry themselves, it'd be really rude to prevent them from doing so by manually wiping them.
• Minimising the time spent in pointless effort for things that will need to be undone. So never making my bed, only folding clothes that really need folding and that I won't use soon, etc.

Random stuff :

• When cooking, making food for several meals at a time.
• Using a rice cooker (or other appliances that cook food for you and that you don't need to watch).
• Using several laundry bags, one for each type of laundry program or liquid, so that it's already pre-sorted and I can see easily if there's enough in one bag for a wash. It avoids going through everything only to find there's not enough black clothes/white clothes/delicate clothes/towels/bedsheets/whatever for a laundry.
• Never using laundry clips. They take too long to put and remove. Instead I use hangers and S hooks, and for the small items that can't be hung on hooks and won't stay on hangers like gloves and socks, I just dump them on a shelf made of metal bars (there's folding ones you can put on a radiator).
• After doing laundry, leaving clothes I will probably wear soon where they hang instead of folding them and putting them in their place only to have to take them out later.
• Having a "to put in bathroom" and "to put in kitchen" basket where I put stuff I need to put back in the bathroom and kitchen, so I don't have to walk there for every item.
• Not putting a duvet in a cover because it's very tiring and I really hate doing it. Instead I sandwich it between two larger bedsheets.

On my computer :

• Keybinding every frequent apps and actions, rofi almost everything else (apps, ssh, file browser in some cases, calculator, unit converter). Saves a lot of time, pain and aggravation by not clicking so much all the time.
• Using 'vim -y' for simple text editing cause I don't have months to spare learning regular vim, or years reconfiguring emacs' shorcuts, just to take some notes or make an ASCII drawing. And nano's shortcuts make my brain hurt almost as much as emacs make my hands hurt. (To be fair, I probably would save more time in the long run by just learning vim but my brain starts going "NOOOPE I'm on strike" whenever I consider doing it ^_^")
• I'm considering trying NixOS because I keep wasting time forgetting if I already configured something, how I did it, what settings I used, etc, and having a declarative config file instead with everything listed in it seems much more practical.