I have been trying to extend my H1B (non-cap) for couple months so that I won't have a gap till my next H1B (capped). If my school won't be able to finish filing my extension petition before my current H1B expiration date, I plan to file H4 visa as a backup, based on my spouse's H1B.
To file H4 while I am in US, what kind of procedure
-File I-539 following the I-539 Instructions.
and documents do I need to prepare?
-Copy of your H1 approval notice with I-94 and her lastest 3 month paycheck stubs; copy of your current H1 approval notice with I-94 and your lastest pycheck stubs; a completed Formm I-539; copy of your marriage certificate; copy of your passport.
Also when do I need to file it before the expiration date (I don't want to file it too early to ruin the chance in case the school can still process my case quick enough for my H1B)?
-USCIS has to receive your H4 application (put it into system) before your current H1 expires.