Some tips and tricks to get the most out of your device

Battery life

Install a new battery in your phone. If you haven’t replaced your battery before, this is probably the first thing you should do.
If you have an S6, install an S7/S7 Edge battery in your phone. Check here for more details, but this can improve battery life by as much as 50%!.
Lower your screen brightness
Reduce your screen resolution to 1080p or lower to lessen load in 3D Games
Disable the hardware navigation lights or use on-screen navigation
Use a wakelock blocker to stop unneeded wakelocks from GMS. (be careful with this one)
Run without Gapps - Google applications are very heavy these days. MicroG is a good alternative.
Use dark mode (AMOLED dark is even better).
Configure battery saver mode to turn on, which limits maximum CPU and GPU clocks.
Limit your charge to 80% to prolong your long-term battery health
Disable fast charging and don’t use wireless charging. Less heat = better battery longevity
Use 2G/3G instead of 4G radios when possible
Use an adblocker when possible

Install GCam Go or Open Camera for an improved camera experience
Use PlayIntegrityFix to bypass Play Integrity attestation checks for banking. Refer to XDA for details as this changes constantly
Install AOSP mods to tweak the way the UI looks
Remove bloatware/snake-oil apps that you dont use
Use cloud storage to maximize your phones local storage
When setting up fingerprints, instead of setting up 2 seperate profiles for 2 fingers, use 1 profile for 2 fingers (50% for one, 50% for another). This is faster than having to setup 2 different profiles
Install my TWRP for OTA updates

Always use updated builds where possible.
Don’t use old Android versions. It can be nostalgic to use Android 5.1.1, but realistically it will be slower, not as supported in newer apps, and far less secure.
Don’t download random sketchy APKs or apps for “too good to be true” claims.

Create backups of your device sometimes - just in case.
Use a case and screen protector - this is super cheap these days and can protect your device
Don’t pull on USB cables. The port is directly soldered to the board, so is hard to replace.