if I have h1b petition rejected in say 2012 quota,

if I have h1b petition rejected in say 2012 quota, how much is its impact, do i need to mention this rejection to new employers or in further consulate interviews, as its petition rejection and not the actual visa rejection

With my H1b denied petition in hand, also please advise what are the best choices I have about further job h1 applications in US.

Do you know the rejection reasons? If it was denied b/c of reasons related to the position, employer etc (i.e. nothing related to you), then you are not required to inform the new employer about it. If the denial reasons were related to you (for e.g. profile, educational qualification etc), then its better to inform the new employer about it so that they can take care of these reasons when filing the new petition.