could you elaborate a little on the temperament comment...
It complicated, but basically... there are two ways to tune your guitar.
Equal temperament - all strings tuned to a standard pitch of 440 Hz (0 cent). For this method simply tune the strings of your lap steel "straight up" on your tuner.
The other way of tuning is Just Intonation - certain strings are tuned slightly flat in order to make the chords sound more "in tune". It’s crazy, I know, but if I tune all strings ET (straight up) and strum across them… the chord sounds slightly out of tune to my ear. It’s very noticeable when recording over a rhythm track, not as noticeable when playing solo.
The 3rd interval and the 6th interval are the most critical, in my opinion. Those have to be tuned slightly flat for the chord to sound "in tune", in my opinion. In the key of C (C6 tuning) that would be the E (strings 1 & 5) and A (string 3).
[tab]
C6 tuning
interval offset
1 E 3rd -13
2 C root 0
3 A 6th -15
4 G 5th -02
5 E 3rd -13
6 C root 0
[/tab]
This is what works for me. It’s important to note that as the bar moves up and down the fretboard playing two note harmonies and other positions, the intervals (root, 3rd, 5th, 6th) are on different strings than they are on the open strings. For this reason not all positions will sound perfectly in tune with the chord the band is playing at all times. An experienced steel player can often compensate for that with the bar. Maybe Equal temperament is a better compromise in this regard, but I can’t live with the sour 6th chord of ET... my opinion, of course.
So much for the "basic" explanation!

There’s really no easy way to explain this topic.