Setup for Slide

Slide for only slide playing or slide for occasional slide riffs?

The gizmo wrnchbndr suggested would be fine if you were only doing slide, but would be impossible for any chord work.

I too switch back & forth from slide to fretted notes/chords.

I set mine up high enough to prevent "fret strike" but low enough for fretting as well. I also use slightly heavier gauge strings.
I used to make up custom sets by taking a standard 10-52 set (52,42,30,17,13,10) and adding a .015 as my B string, and shifting the .013 to the the E1. (I just kept the 10 as a spare for other guitars.) I should mention the majority of my tuning is open E & D.

I eventually found the 17-13's too heavy for bending if playing single fretted notes for lead or chords (particular w/ open E). I now have gone to 11-49's and just a slightly higher action than my standard tuned guitars.

I presently use a LP-style guitar for my open tune slide stuff and I set the action at approximately 2mm at the 12th fret on both E strings. My TOM bridge is fixed at 12" so in this case I get a completely parallel radius. The usual action I aim for is E6 @ 1.6-1.75mm and E1 @ 1.5mm.
Not a great difference number-wise, but a big difference playing-wise. (for me anyway)

When I set up a strat for slide I also set the strings to a radius consistent with what ever the fretboard is. Some like it "flat" but I find I can isolate single strings better with a radius by changing the angle and position of my slide to the strings (if that makes sense).
And even with the radius I can still play multiple strings simultaneously for those sliding "chord" sounds.

Everyone has their own way that works for them. This is what works for me and may help you find yours.

Happy sliding!

If you're gonna raise the nut, just buy a lap steel. The beauty of slide guitar is being able to fret notes as well.Use heavier than normal strings,gauge depends on whether you tune up or down, say E versus D. Raise the action just enough to clear frets, but be able to fret as well. Listen to old cats like Robert Johnson,or Sunny Landreth for a lesson on how to play notes behind the slide.

I think by "behind" the slide he actually meant in front between the slide and nut.

Players that wear the slide on their ring finger can and do fret behind the slide with the pinky finger.

Sonny Landreth is a "pinky" slide player so he gets 3 fingers in front and can fret more complex chords.

I'm a ring finger player but don't do anything with my pinky. I'm just not that clever 

It was Sunny I meant when the behind the slide was mentioned. Johnson just because he's a great foundation for the technique. What Sunny does is while engaging the slide, he pushed down between the slide and nut, releasing the slide from the string and hitting the fretted note. For instance, in an open E tuning, depressing the g string one fret this way makes it into a minor chord. He is truly a genius, I never knew of anyone doing that before he came along. It opens up tons of possibilities. Another great slide player is Ry Cooder, he uses open tunings, but the key center is often the 4th of the chord,which makes the open chord the 5 chord of the song if that makes any sense.

Here's a vid of Sonny explaining some of his technique. I've had the pleasure of seeing him play a few times and met him once at a small gig for BMG Records; he is the most humble guy ever. And he is insanely good on slide. You can hear one note from a Landreth song you've never heard before, and you know it's Sonny.