Pulling off a trade in fantasy football is no easy feat as there is often a struggle for the two parties to agree. The best way to approach a trade is consider what you need and what you have an abundance of. For example, if you are in need of a good RB1 and have two really good WR1s and solid WR2, you should consider trading a WR for a RB. The next step would be to find someone in your league who needs WRs but has an abundance of RBs. This isn't a fool proof system but probably the best way to approach a trade.
The goal should be to find a deal where both owners feel like they "won" the trade, and even if the other owner is getting the "better" side of a deal, doesn't mean the deal isn't beneficial for you too.