I was just wiring some rotary pots today and caught a mistake on the first one. I always have to strain my brain to make sure I get them right. If you’re looking at the pot from the front with the pins downward, pin 1 is on the left and pin 3 is on the right, and the wiper is shorted to pin 1 when fully counterclockwise. So for a voltage divider normally you want pin 1 at ground and input voltage on pin 3. For a variable resistor you want pins 1 and 2 if you want resistance to increase as you turn clockwise, 2 and 3 if you want it to decrease.
(In the Gate Grinder there are two pots and I wanted one to control the clock rate (low to high) and the other to control the gate width (short to long), and if you think about it that means CCW is long RC time in one case and short RC time in the other, and managing to get that right the first time on the PCB I considered a personal triumph.)
Never used slide pots but I think I’d have an easier time keeping them straight, since the proximity of the wiper to each end is immediately visible.