Here's the list, you don't have to do all of this, for example I disabled Samsung voice because it's not useful for me.
1.Disable GPS, Bluetooth, NFC and turn them on when necessary
2.Disable Wi-Fi calling
3.Disable voice over LTE : on phone application go to more, settings. Find Voice over lte settings and set it do not use volte
4.Disable all motions: settings, motion and gestures, turn all 4 options off
5.Disable SVOICE and Shealth app
6.Disable all Google useless services
7. Use black wallpapers for screen and lock screen
8.Go to location setting and turn off Google location history
9.Turn 4g data off when using Wi-Fi or don't need Internet
10.Turn useless vibrations and sounds off
11.Go to developer settings and turn all animations off
12.Go to Wi-Fi settings, more, advanced and turn always allow scanning off
13. Use auto mode for display light
14.If you don't using Samsung printer service Disable it, on settings, connection, more connection settings, printing, Samsung print service plug-in
15.This is just an advice, don't use more than one application for one task, you don't need 2 calculators or 2 pdf readers and so on..
16. Use clean master every week and Uninstall it after that. Just clean junks with it
17.Turn backup data and auto sync off
18.Go to smart manager, ram, manage apps and auto stop apps you don't want to run on background, for example an application like what's app needs to run on background but games or pdf readers don't.
19. Do not use Google Chrome if you can. The default browser is so good and support fingerprint sign-in which is a nice feature.
20. Be smart, use do not need Gmail app,yahoo mail app, and ... to manage your emails (this is just an example) you can install an application like k@mail to control all your email accounts with just 1 application , same thing for note taking and ...
Hope you find this useful, tell me if any of this tips worked for you.