Crunches (sit-ups) I do everyday up until 400 (altogether on left/right/middle with legs in the air; knees bent), I do them until my chest reaches as high as it can get.
Push-Ups, I go for a minimum of 50 and stop whenever I cannot do anymore. It's best to add a few more than you did before so you know you're improving.
Pull-Ups, I plain suck at this, I have no upper body strength to go above 10.
Bench Presses are easy up until 240 pounds when they actually make my arms shake.
I prefer running over the rest since they're muscle building and require constant rinse and repeat to stay the same or else you lose it all. Running does it all, and with weights in hand (preferably dumb bells of 10-20 lbs. each) it does the same thing to make you look good.
