This one is going to be really quick.
In Part 4, I recommended printing some trees out on overhead transparencies so that they can be scattered at will over maps. You can also do the same for blood splats and use them to mark the places where an enemy has died.
If you're not of a sufficiently artistic bent to create your own convincing blood splats, there are lots of downloadable Photoshop brushes out there to help you out.
Make sure you make lots, both big and small. If nothing else, the big ones are fun when someone is killed, shall we say, very thoroughly.
Stay tuned for Part 12 - Dungeon Mastery.