LOL I always unroll the paper, put the box on it and figure out which way it'll wrap the best using the smartest use of the paper, horizontal or vertical. Put a dot where I want to start the cut and then cut off the roll. Pull the paper around the box and then trim off the excess if there is any. The only time I ever had too little paper is when I had to wrap something really huge and there wasn't enough paper on the roll. Then it looks like patchwork wrap trying to find another paper that'll match it.
I used to be a wrap-a-holic, because I had the time to do it. LOL I would do the fancy ribbon wraps and make all those wild bows. Had a ton of fun with it, till I got to Noah's 4th Christmas. That's when the presents under our tree stopped looking fancy. LOL I always end up running out of time to wrap, so the paper may be on the box, but it takes soooo long to do the ribbon, when I'm the only one doing it - it's Christmas morning before I'm done. His 4th Christmas I was up till 4am doing the ribbon. He got up at 6. Got us up, and immediately dove into it. Then when he was older I started again, and he asked me not to do it anymore, because he said they were so pretty he felt badly undoing the time I spent making them. ROFL