Easiest answer is ALL OF THE ABOVE. You are trading with and individual so the two of you have to be happy to make the trade work. Face for Face is a good baseline. I am sure you will find a lot of people that would be happy to take 5 of yours for 1 of theirs or the other way around. The important thing to keep in mind is that they have something you want and it is best for both of you if you give them somthing that they want.