Welcome to softball umpiring! Hope you have a blast with it!
As for the strike zone, I'm assuming you are referencing fastpitch softball. My clinicians have generally said "bring it up, bring it down, and widen it out". In explanation, generally nothing above the letters, nothing below the knees, and full width of plate. If you can access this site -
http://www.ncaa.org/library/rules/20...ball_rules.pdf
there is an excellent diagram of the ideal strike zone within this rulebook.