I know this may sound a bit basic... but watching films like Black Hawk Down and Saving Ryans Privates can give you basic hand signals for use on the field.
As Rider-in-Black said, best tactics in Woodsball are good use of communication, and keeping these as simple as possible will allow you to communicate with others even if they are not your immediate team mates.
Finger to mouth (or mask) = quiet...
Flat hand being lowered = keep down...
Two fingers to eyes then pointing = look over their..
Chopping hand action in a certain direction = request for covering fire in that direction
Point to gun then finger across throat = marker not working...
Curling up in a ball = oh poop I've been hit in the family jewels again...
Just a few (good) examples I hope....
It's not rocket science, so should work for most, even for the guys that have failed to use the written english language on here...