Hello!  I'm going to be heading out on a big camping trip and will need to take some extra supplies.  Are you going camping as well?
I am also going camping! What do you think you're going to need the most of? What are your preferences?
It's going to be hot during the day where I'm going so I'll need some extra hydration.  So water is my main priority.
Got it! I am going to need the most of food. There aren't any animals or berries that I feel safe eating where I'm going.
Well I think we can make a good deal then.  How many packages of food would you want?
Could we each do 3 of what we need the most? I get three food and you get three water? How do you propose splitting up the firewood?
We can do the 3 for 3 trade.  That works perfectly!  Its' going to be cold at night where I'm going.  What's it like where you're heading?
It's going to be pretty warm where I'm going, but it's also variable. How do you feel about you get 2 wood and I get 1?
That's mighty kind of you.  We have a deal!  I'll take the 2 wood and you get 1.  Thank you.  You'll also get the 3 packages of food and I'll get the 3 waters.  Deal ?
Deal!