When things go south, I tend to scream, yell--sometimes I even hit things or even myself.
I'll just smack the top of my head or something.
I usually just rant in mindless blabber about what they're doing wrong, and when they do something right, I yell "C'MON!!!!!!!!!!!" or a short Russian word (davai/lichna). Then I start insulting them for not doing it more often yet.
Include lots of fist pumps, mocking the opponent of the woman I'm supporting, wanting them to die, etc etc...
These reactions are for a select few, though. Elena, Dani, and Venus primarily, and sometimes just depending on the match for my other favorites. If Vera or Aga or somebody loses, I don't get too worked up on about it usually.