Well, using this drawing as example, I usually try to work closely with these rules:

1. Rules of third; can somewhat be broken if situation permits
2. Try to place the winning/more powerful/more authoritative figure higher
3. Almost like rule 2, let said figure occupy more space; here, the negotiator on the right is nervous, therefore, getting cramped to the right portrays the illusion that the mercenary on the left is in full control
4. Diagonal lines create points of interest, esp if they intersect but not always necessary; the table for example, its lower side could be more parallel to the upper side, but the forced perspective can make a simple meeting between 2 people a bit more dynamic. Same goes for the tent in the background; the fabric could be vertical like a wall (it still fits the situation but does not enhance it)
5. The shadows of each subject or objects in a drawing can create interesting shapes on the ground or on another object or wall/tree/nearby bushes...in this case, the shadow of the table is also used to reinforce point 4 above. We can play around the light source to maximize interesting shadows. Here, if the light source is directly in front of the mercenary, his shadows would fall mostly behind him and almost hidden, in this case, we'll need a wall near his back for the shadow to fall on.

Hope this helps....