Both have 4 days prep, Both have info on each others past feats. But only know a little bit of actual personal info on them.
Both can use all the resources they have. With one exception neither is allowed call in outside help. (For example Emiya cannot summon Saber to kill John and John can't call up any nasty demons to tear Emiya to pieces. Other then that both are free to use any magics/weapons or tactics they please)
The location is a small empty country town
Both are aware the other is in the area
Win the battle by death/knockout/BFR/capture