What is "launch" exactly? Do a Show HN. Tell all friends/family you're live and to start spreading the word. Email your personal networks and do the same. If you have a mailing list, let your list know you're live and ready to go.
Start getting feedback as soon as possible and don't ever stop listening.
We did the part of telling our friends/family when we had the closed beta ready, but there is a big difference for us between the closed (free) beta and an open beta that can accept paying customers.
Can't go into specific at this stage but imagine we're building an iOS app and waiting for Apple to approve it (not our case but close enough)