Trance, concentration and the "vibrations"

Hi There,
I was hoping on some clarification on what I've been experiencing lately. I've been practicing trance work, energy work and projection on a daily basis
now for a few months. I've managed to get some helpful astral experiences, BUT I haven't once yet had a wake-induced conscious OBE exit.
Its this process that Im really striving for, so I can understand and teach my body how to do this regularly.
So Lately I've been getting into a trance state, after some energy work and then picking something to concentrate on. Usually my breath, or my heartbeat.
I've also been working hard on my mind-taming techniques, but still have a ways to go Im sure. I can get about 45 secs without mental chatter.
As Im trying to hold this concentration, its only when my mind slips away, that the vibrations set in. I feel my arms, or legs or chest start vibrating, and then it pulls me back to consciousness. Then I try to use the 3rd eye trigger or other concentration to keep the vibrations going but they slip away.
This happens consistently, so much so, that I've begun to try to get my mind to wander, in order to teach myself to grab consciousness as the vibrations set in on the exit.
Can the vibrations be induced through concentration? Perhaps very sharp concentration? I also usually get exit symptoms when doing the full-body circuit but they usually come and go randomly.
Any help here would be awesome. Thanks a bunch!

What I would tell you is to not 'try to get vibrations', because they are not always 'windows to exit'. They are signposts indicating that your awareness is shifting, and the object is not to 'make the vibes stay longer', but to get deeper into the trance, and ignore them or slow them down -'smoothing them out' is one way it's been described- until you then start trying some exit technique. If you concentrate on the vibrations themselves or focus on them as your mission, you then centralize your focus on your body when what you're trying to do is externalize it. So I'd consider vibes a time to start working on either energy body loosening or exit, depending on how your awareness is changing (are you 'seeing through your eyelids, seeing other beings, seeing/feeling what you think of?) and if you can move your body, it's just too soon.
As to using imagination to 'zone out' enough to get tranced out enough, that's ok to do, as long as you can recognize when you start drifting off and be able to bring yourself back 'online', so to speak. Doing this (letting your mind go) can lead to click outs, but you can do it if you can bring yourself back when things start getting dreamy.
I hope this was helpful.

CFTraveler, Thanks alot for the reply. It helps get my focus in the right area's and clarify's a few things
for me. Thanks a bunch. I'll redouble my efforts.
Safe Journey's!