three man mechanics

[refjef40]

I'm in my fifth year of H.S. ball and am fortunate enough to be doing my first play-off game.I will be at third base but I have never done three man before.My question may seem silly but I would rather ask here than at the pre-game.Is there any situation other than a runner on first that i would be in the slot at second?I believe with first and second I'm back at third.Also any tips about the third base umpire that you veterns have would be apprieciated.Thanks in advance.