I never really plan sets or mixes.
I tend to listen to the new tunes from beatport etc. on a Sunday night, usually end up with around 50 in my cart, then listen again and get them down to around 20-30.
Then listen to them in bed all the way through (well as long as the clip is) and ditch the ones I can imagine I would get bored of, try and get 12 per hour.
Then drag them into iTunes and flick through them, no longer than 10 mins or so to put them in some sort of order.
I then know what order I can play them in, only time I tend to swap is if they are not in key when cueing it up, so I will grab the next track instead and hope the one before works with that.
The only mixes I have really planned over the last 5 years I can think of, was the Silicone Soul Collection mix I did, my take on Involv3r, and my Zoned Out mix I did recently.
That doesn't mean I haven't gone back and done it again if there is an annoying track or transition in there. But I don't plan them.