I like people to take their big breath in after step #3 and before step #4. But this isn't graven in stone. As a recent thread on Rip's Q&A discussed, some people can't get a good breath at the bottom and need to take their breath while still standing up. There are several ways to skin this cat. The important parts are:
1. Have a hard valsalva while the body is under a load
2. Squeeze chest up hard so the entire back, lumbar and thoracic, is in hard extension, before pulling