I used to be able to induce vibrations very well but i stopped practicing astral projection for some time and cant remember quite how to do it any personal ways and techniques would be interesting to hear.
http://www.astralpulse.com/forums/welcome_to_out_of_body_experiences/vibrations_a_theory-t32920.0.html
Empty mind meditation daily + Hemi-sync..
You don't always have to experience vibes to project. The main aim (and the only aim at least for me) is to have an OOBE.