Lindsay was about 7 months when he started doing that, and then he was crawling by 8 - 8.5 months. The girls never rocked on their hands and knees at all and Erin was crawling at 4.5 months (trust me - never wish for an early crawler!) and Paige was crawling at 6 months.

As for crawling before sitting, Lindsay could sit on his own before he could crawl and Erin was 6 months before she could sit upright on her own. She would just prop herself up on one arm to sit. Paige started sitting and crawling in the same week.