One trick I figured out is not to be stingy with either paper or tape. Use a larger piece of paper, or several pieces taped together, than you think you'll need. You can always fold away or trim off excess. Liberally use tape to hold flaps and folds in place.

Another trick is to practice with paper grocery bags. They're much sturdier, thus more forgiving of trial and error, than typical wrapping paper (never mind tissue).