Here are a couple things I've thought over the years.
1) Don't plan a trade beforehand, that just makes it pre-planned and makes it look dumb.
2) Find a team that is at a spot where the best player available doesn't fit a need, and see if a trading partner exists. It's best to look for teams with a history of not being afraid to trade.
See if the trade would be a good fit value-wise. You can google "trade value chart" and it will bring up what each selection is worth. Try to get the value as close as possible and see if it still seems likely for a team to do it. *If including a player, try to think beforehand what value that player would be. If trading Michael Vick, think what someone might trade for Vick. Is a 3rd round pick a reasonable draft pick for the a soon-to-be 33 year old QB with a history of injuries? This is all stuff you will need to consider.
Now, we all know predicting a trade is nearly impossible. There's just too many factors that go into it. For the most part most of us will not give you a hard time for trades because it's something you are doing to try to make your draft different from other peoples.
The best thing to do is just make sure the trade makes sense for both sides, make sure the value of the trade is fair and then just make the best selection you can.
It's kind of irrelevant now, but as the real draft approaches take a look at who teams sign in FA and listen to rumors on what FA's the brought into visit. Also keep track of what college players they talk with, and for things like the SR Bowl, remember what teams coached which sides. There are many times a team takes a player they coached in the sr bowl.
For example, last season I heard many rumors of the Eagles liking both Dontari Poe and Fletcher Cox, so I had them trade up to #9 in my mocks before the draft to grab one of them.
In the end, the Eagles did trade up from #15 to #12 to select Cox.