There are standard recommended settings that get copied and pasted a lot.
Short version:
Settings>System>Display>Resolution> 1920x1080p
Settings>System>Display>Whitelist> (empty)
Settings>Player>Videos>Adjust display refresh rate> On start/stop
Some televisions may also need, or benefit from, the following being set…
System>Display>Force 4:2:2 colour subsampling> (enable)
More advanced users might like to experiment with the whitelist function. A guide to that can be found here.