If you use a tiering system, trade players in a tier for players in the same tier and a bump somewhere else. If you really do value the "good" players equally, you're basically getting your prospect for free. And even if you don't, you might start up trade talks on something you like - maybe you swap a good player for their equally good player and a second.
Like let's say you see Wes Welker and Roddy White as basically the same guy. That seems reasonable to me - both of them were injured last year, but both are very valuable when healthy. In fact, you could make a case that Roddy has more VBD left because the Falcons are looking to sign him to a contract extension, and Welker's in his last year with the Broncos but there's been no word about resigning him and they just drafted a receiver and added a young slot type guy in free agency. But Welker's got the Manning factor working for him, and for some owners, that has a huge amount of trade value. So you float an offer out there of Welker and Scott Chandler for Roddy and Kelce, or Welker and Woodhead for Roddy and Khiry. Who knows, maybe the Khiry owner really likes Woodhead, and accepts quickly, thinking he got the better end of the deal. And now it'll be a lot easier for you next time you want to make a trade with that guy, because he loves the offers you send.
If you're not sure which trade to offer up first, and you like all those prospects about equally, the first thing I'd consider is where you have your biggest depth issues. I like to have one more borderline starter than I need for my starting lineup, so my team doesn't get decimated if one guy busts or gets hurt. Roddy owners last year can tell you how valuable it is to have a solid backup WR who they can put in the lineup while they're figuring things out - a lot of guys started him for several weeks waiting for him to get better because they had nobody better to put in their lineup. Ditto Trent Richardson owners. I don't even consider TE depth - it's almost impossible to play matchups or streaks with tight ends - but in your case, a fourth receiver might be more helpful than a fourth running back unless you start two of each or something. Absent that, given the choice, I'd always take the RB over the WR just because mid range RBs are way more valuable than mid range WRs.
Last but not least, leave room for waiver pickups. In your case, you've only got two trash players. Steve Smith, who's been "too old" for like five years now, and Scott Chandler. Woodhead isn't trash in a PPR, but he wouldn't start for you unless you had serious injuries. I personally think Riley Cooper is borderline trash, and I think he's got solid trade value right now, but you might not. Vick is borderline trash if Geno ends up starting, but it's hard to drop him when you've got Geno and a non-elite QB1. When the season rolls around, you want a dead spot or two on your roster so you can pick up a free agent. If you're trading for someone you're not going to be willing to drop, then you need to figure out whether you'll have someone worth dropping or trading later. For example, if you hear any positive press whatsoever on Steve Smith, try to trade him to a WR needy team for a future third or fourth round pick to free up a roster spot.
