Each of my kids has learned to crawl in different ways.
G-man took forever to crawl. He just wasn't interested in moving anywhere in particular. Our apartment was small and mom provided for his every need, so why bother? Finally at 9 months I bribed him to move with Cheerios in a line across the floor. He started out military crawling and shortly thereafter moved on to the real thing.
Kiwi started crawling at 7 months and a week later started pulling up on furniture. She was not going to be left behind by her big brother if she could help it.
Mr S has gone in his own direction on the road to becoming mobile. Our home is mostly tile, so he has devised an ingenious way of pulling himself across the floor. Thus we have re-christened him Scooch in celebration of his new found mobility. A friend (yes you Katy) mentioned he looks like he's got a bum leg he's dragging. In true boy fashion he is chasing a ball in this clip.