Get approval BEFORE resigning!

1. When I was transferring from L to H 3 years ago the lawyer for the new employer told me not to notify the old employer yet, because what happens if you resigned but the new H-1 petition does not get approved? Then you are screwed and no body can help.

2. Lawyers have different interpretation on when you can start working for the new employer. If there is not rush, I'd be more conservative.