Debbie, whatever else you do, definitely do NOT use chicken wire; you want a cage that you can reach into to pick the tomatoes (and to retrieve any that happen to get knocked off onto the ground).
I have big wooden cages that we built from 1x2 and 2x2 lumber (actually we cut everything from 2x4's). You could probably construct the same sort of thing from branches, if you were so inclined.
This was in early spring, with plastic still wrapped around the cages; they measure approx. 2' x 2' and about 5' tall (some of them are actually double cages that measure 2' x 4'). Easy access for picking, weeding, etc. We formerly used cages made of wire fencing with holes about 3" x 4" or so, but sharp edges from where we had cut the fence left me gashed up and bleeding every time I picked tomatoes!
