Even something as basic as setting the Player Size to "Big" and your preferred Video Quality (720p for me) as the default is not something I figured out how to do with just Youtube itself. I'm doing it every time anyway, why can't Youtube just let me set my own defaults?
So it's up to users like eugenox to fix this for easily annoyed people like myself. And maybe you as well:
https://greasyfork.org/scripts/593-yays-yet-another-youtube-script
Code (link posted because incredibly long): https://greasyfork.org/scripts/593-yays-yet-another-youtube-script/code
Instructions:
1. Install the Greasemonkey Extension for your internet browser
Firefox: https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/?src=search
For Chrome, you can get TamperMonkey, but keep in mind, I have not tested this script for Chrome:
https://chrome.google.com/webstore/detail/tampermonkey/dhdgffkkebhmkfjojejmpbldmpobfkfo?hl=en
2. Install the Script: https://greasyfork.org/scripts/593-yays-yet-another-youtube-script
3. Visual Aid: http://i.imgur.com/K1r0PJN.jpg
Go to a Youtube video. If you scroll down to where the thumbs up/down, about, share, add to, transcripts, statistics and flag tabs are (see visual aid), you will see a new "gear" icon, which will now be your new youtube settings. Click it.
4. Set your preferred settings as you want.
Done. Enjoy not having to do needless tedious clicks every time you watch a youtube video.
More stuff like this from me:
Whitelist by Youtube Channel - GM script (UPDATED): http://www.teamliquid.net/blogs/460015-whitelist-by-youtube-channel-gm-script-updated
Watch Twitch/DM on VLC/MPC(good for low-end users): http://www.teamliquid.net/blogs/445573-watch-twitch-dm-on-vlc-mpcgood-for-low-end-users
How to get Twitch to play on SmartTVs via Serviio: http://www.teamliquid.net/blogs/437509-how-to-get-twitch-to-play-on-smarttvs-via-serviio