so, you have two feet, right? That's good cause it's one hell of a lot easier that way. One foot (your choice which one) stays in the pedal pretty much all the time. I almost never remove my right foot from the toe clip when riding, even at stop signs and the like, it just hangs out in place. Because it's not going anywhere, I can tighten the strap down more than the left foot. This keeps in it place better, and allows me to pedal in more of the circle.
For the left foot (or it could be right) you have to treat it a bit differently. For starters, you are going to have to enter this toe clip while moving, which takes a bit of practice. I suggest starting with the arch of your foot on the bottom of the pedal (opposite the toe clip) and moving it backwards in a scraping motion. This usually flips the pedal upright, allowing you to slide your foot in. Remember, Practice makes perfect.
Once your left foot is in, you can reach down, and pull the strap to cinch it down. However, this means you might have to loosen it before coming to a stop, which is a pain. Try and find a happy medium, where your foot is held in place, but can still be easily removed.