Setting the intonation on your guitar is really important if you want your guitar to play in tune wherever you are playing on the guitar neck.
However setting the intonation is always a compromise and it’s about trying to get the best overall solution for your guitar.
Basically for each string we tune the open string to the correct pitch and then fret the same note but at the 12th fret and compare the two notes.
If the Fretted note is Flat move the saddle for that string Forwards (towards the neck).
If the fretted note is sharp move the saddle backwards (away from the neck).
Remember FRET FLAT FORWARD.
In this video I demonstrate how to set the intonation on a strat style electric guitar.