Well before I worry about metrics and stuff too much, I consider the approximate player tiers for the guys in question. I know this sounds dumb, but I think of it like chess, where you don't get too in depth right off the bat when its your move. You consider your possible moves and whittle down until you have serious contenders, then do the extrapolation.
I say that to say this. I come from a different cut of the cloth than a lot here, but I really place a lot of emphasis on league economics. I.E. you can argue all you want that you "should be able to get player x, y,z" but distribution is similar in the fantasy world, but differs enough that you might have to overpay to get a certain player, or conversely the would be partner wants too big of a price back relative to values.
So when I offer a trade or look at one offered to me, I evaluate the type of trade in general -- power for speed, or lumber for arms. Then I think about the tiers of players that should be involved. Abject stud, b tob plus talent, spare parts, speculative plays, and then the junk transaction. To me it sounds obvious, but I frequently find that behavior doesn't reflect that. Then I scour the rosters and see what other teams could sync up in a similar way, and how players make up the unique universe of that league. And with that, I get a feel for how much I have to pay to get a need. A lot of times I find that you can run projections all you want and try to trade based off of that, but many times you only have a few potential partners for any given type of trade.
So I will let the stat guys give you in-depth look at metrics, but I generally only get involved in that if someone is either really green, or outlying what we generally conclude about said player. When we are dealing with established guys, I prefer to rely on the soft skills of trading and big picture. It doesn't bother me if I don't extract every last ounce of blood in a trade, if it adequately improves me where I need, and doesn't devastate the opportunity cost of player value. (Like if you trade a first rounder, if there are a couple of teams with a couple of player packages that would be satisfactory, I don't drive such a hard bargain that you sully the field. Maybe I'm a fool, but I have generally had good results with taking an overall stock, and working down from there, then relying on the more advanced stuff to break a hard decision, or shed light on a player i'm not overly familiar with.