Nine settings decide how long your Android lasts, and eight of them ship switched the wrong way. Menu names below are Pixel's; other brands sit close by.
Settings > Battery > Battery usage, then View by apps. Before changing anything, see which app actually ate the day. Usually one app is doing most of it.
Settings > Apps > See all apps > the app > App battery usage. Set Allow background usage to Restricted so it stops waking your phone while you sleep.
Settings > Display & touch > Smooth Display. It pushes the screen to a high refresh rate. The screen is the biggest drain on the phone, so this is the big one.
Settings > Display & touch > Always-on Display. It keeps pixels lit every minute your phone sits face-up on a desk, for a clock you already have on your wrist.
Settings > Display & touch > Screen timeout. Most phones idle at 30 seconds or more. Drop it to 15 and every put-down stops costing you half a minute of screen.
Settings > Display & touch > Adaptive brightness. Leave it on and stop riding the slider at full. Manual max brightness indoors burns power for no gain.
Settings > Network & internet > Adaptive connectivity. It drops you off 5G when you do not need the speed, instead of holding a power-hungry radio all day.
Settings > Location > App location permissions. Change anything set to Allow all the time over to Allow only while using the app. GPS is a constant drain.
Settings > Display & touch > Dark theme. On an OLED panel black pixels are switched off, not lit. On older LCD screens it looks nicer but saves nothing.
Adaptive Battery, under Battery > Battery Saver, is the one to keep on. It learns which apps you ignore and starves them. Turning it off makes drain worse.