Improve your SOT (for mobiles AND laptops)

Some of these tweaks are purely subjective, and might not show consistent results across devices

For mobile phones running Android:

Non-rooted/Stock users:

1. Turn off anything that relies on "AI," like automatic brightness. Those things claim to save battery but actually keep more sensors active.
2. Turn off location when you don't need it. You HONESTLY don't need a GPS connection while watching YouTube or using Spotify or texting on WhatsApp. Turn it on only when needed.
3. Manually control brightness as per requirement. Keep dark mode on at all times, and adjust brightness if you can't see. If it's too bright out, turn off dark mode and reduce screen brightness.
4. Turn off unnecessary vibrations. Pretty self explanatory. It may not seem like much, but when you're a massive texter, it helps. Also, unnecessary sounds like keypress sounds.
5. Regularly uninstall apps you don't use. Sometimes background processes eat up battery.
6. Use earphones (wired, not bluetooth) whenever possible. Since the speakers in earphones are smaller than the device ones, less power is consumed.
7. For the extra edge, keep Battery Saver on whenever you can. Turn it off only when you have to turn off dark mode as mentioned in point 2
8. Keep glance/always on display/pickup to wake off. It keeps the proximity sensor and display running, drawing more power.

For Rooted users:

1. Try and switch to MicroG. Data Privacy + lesser background services helps.
2. If you need GApps, use BiTGapps. It's much more battery efficient than OpenGApps because of the optimization patches
3. Flash a custom kernel that's battery oriented. Pretty self explanatory.
4. Use the Full Set of Francisco Franco apps - FKM, Naptime, and Servicely, and make sure they are set up properly.
5. Manually tweak settings in a kernel manager to reduce supplied power to hardware. DON'T make changes if you're unsure of what the settings do. If you somehow brick your phone, I'm not responsible. 

I personally used ALL these tweaks and managed to boost my SOT on a 3000mAh battery from 5 hours to a (personal/device) record high of 9.5 hours. My usage included heavy social media, occasional YouTube, near-constant Spotify playback through wired earphones.

For laptops running Windows:

Linux users can figure out better tweaks than I can for their platforms and hardware. These tips are for maximizing battery life without compromising on performance

1. Uninstall Bloatware. Some of these apps can run in the background, which might affect performance
2. Disable as much Telemetry as you can. Windows 10 Pro users have more control over this than Windows 10 Home, but disabling even basic telemetry helps.
3. Take control of your refresh rate/check if high refresh rate is being used even on battery power. You don't need 144Hz while scrolling through Twitter, 60Hz should do fine. Enable high refresh rates when needed, disable when not.
4. Turn off keyboard backlight when not required.
5. Control the screen brightness as per ambient conditions. You do not need a fully lit display for watching that movie in the dark. Reduce the brightness to a comfortable level but not too much that you struggle to see the screen.
6. Use earphones/headphones instead of the inbuilt speakers when possible. Lesser power is consumed this way.
7. Turn off Bluetooth/Wi-Fi and turn them on as per requirement.
8. Don't keep your laptop plugged in all the time when working. If you can unplug and still continue to use it, do so. A constant stream of charge will only harm the battery.
9. Take control of your power plan. This doesn't mean you must create a new one - stay on your device's "Balanced" power plan and tweak it. I CAN provide my current power plan that works wonders for me, but do not come at me if anything happens when you use it. IF you want to import my power plan, download the file, and run the following command in an elevated (admin) command prompt -> powercfg -import "path/to/PowerPlan.pow"
10. Unplug external devices like keyboards and mice.
11. Frequently close open applications and unrequired browser tabs. Frequently clean your drives of junk files.
12. Disable all third-party start-up applications. Check for running apps in the left taskbar panel and close the unnecessary ones.
13. Tune your device to use the dedicated graphics card only when required. Every device has different ways for setting this, but ideally, you want to keep the dGPU inactive when there isn't much activity. The system loads processes onto the dGPU when required, and you should see no performance impact.
14. Use the inbuilt battery saver mode to squeeze the last bit of battery life from your device. You can also have battery saver on all the time and see no big impact on performance.
15. Under-volt your CPU (ONLY if absolutely necessary). If you notice power/thermal throttling taking place, under-volting your CPU is the best way to get the most out of your device AND reduce device temperatures. Under-volting GPUs should also see similar benefits, though I haven't tried it/needed it on my device. Plenty of guides for this online.
16. Make sure you're using dual-channel RAM. It gives better performance overall.
17. Clean your machine once every 6 months. It's good to clean your device and maintain it well, but do make it a point to clean the cooling system, since a dirty cooling system will lead to an inefficient cooling system, which means your device won't be able to utilize it's full power because it won't be able to lose heat efficiently.
18. IF POSSIBLE, re-paste your CPU/GPU once a year.

I personally used most of these tweaks on my Acer Nitro 7 (i5-9300H, 8GB 2666MHz DDR4 single channel RAM, Nvidia GeForce 1660 Ti Mobile 6GB) and saw a significant boost in battery life (from a measly 3.5 hours to a solid 7 hours). My usage includes casual gaming (Witcher 3, Quake Champions, Stardew Valley), Programming (having multiple tabs open, basically), Heavy YouTube, Constant video calls, online classes.

AGAIN, use these tweaks at your own risk, and if you hold me responsible for a BSOD in online class or broken alarm on your phone, I WILL laugh at you.