This one is tough. I can't say I have any sort of strategy, and whatever strategy I do have for this will fluctuate wildly from year to year.
The best generalization I can make is that I will NEVER trade a future 1st (any first from any team) for any current 2nd round pick. Barring an extreme example of a player falling to pick 2.01.
I WILL trade a future pick a round higher on occasion, say a future 3rd for a current 4th, if I think an available player is worth that.
It's a bad habit to get into though, because you are giving up value every time you do it, which isn't good in dynasty. That future 3rd you give up could be a player you value as a 2nd rounder, or you could trade it for later future 2nd to someone. Either way, to me, not a good strategy to consistently give up better picks for worse picks.
As for trading picks in the current draft for a higher pick, I have no problem with that. I would rather give up a mid 3rd and 4th to move into the late 2nd or early 3rd than give a future 2nd to do it.