All Immigration forms may be found on the USCIS website.
Most common forms required for Immigrant Visa petitions and applications are:
• DS-230 parts I and II • G-325A Biographic Information • I-129F Petition for an Alien Fiance • I-130 Petition for an Alien Relative • I-134 Affidavit of Support • I-140 Petition for an Alien Worker • I-864 Affidavit of Support (I-864 A, EX, P, W)