There is good advice alrea

There is good advice already being provided here, I’d like to just add a couple resources that you may already be familiar with.

http://www.videomaker.com/article/14564/– Here is an article on the 180 degree rule, which is quite applicable for your dialogue scenes

http://www.videomaker.com/learn/production/cinematography/camera-angles/– this link is a click or two away from plenty of reading on angles

and try checking out some video examples with this video on angles –http://www.videomaker.com/video/watch/tips-and-tricks/531/camera-shots-and-tricks/

I wish you the best with your zombies