stream entry, aka 1st path, the 1st stage of enlightenment, is marked by a cessation. In a cessation everything, every sense door, blinks out for a moment. It's not particularly remarkable, in fact in many ways it is more of a non-event. For most people, if they even notice it, they might say to themselves, "what was that?" - that little blip.
No big deal. But it is a game changer for meditative progress, so let's make it a big deal for a moment. Experiences vary, but for me shortly after stream entry I became mildly aware of the first 4 jhanas, and within a few more months I had all 8 jhanas. That's kind of a big deal. Without stream entry, that progress typically takes a tremendous amount of dedicated practice, hours a day, often for years. And with jhana practice comes great tranquility, and with stream entry the potential for great insight begins in earnest. Something has been let go of or seen through at a fundamental level.
A good vipassana technique such as the Mahasi style will get you in the ballpark of stream entry. There is some groundwork to be done, but if you've been practicing daily for a year or more, you're probably already in the ballpark (technically, the stage known as equanimity in the progress of insight as described by Mahasi or Ingram).
Once you are up against the wall of stream entry, you just need a moment of grace to fall into a cessation. How do we stack the odds? With good meditative practice. Some fine points:
A-R-O: The Arrow, a checklist:
A is for Aware: We want to be aware and present, rather than embedded or lost in thought. Here and now, just this right here, not off over there in thought. We want this awareness to be happening a very high percentage of the time in meditation, or even off the cushion as well. Thought is not necessarily an enemy, so we don't need to resist it or push it away, but at the same time we don't want to feed and nurture the wandering, spacing out mind, we are trying to stand somewhat apart from that, to let that be.
R is for Relaxed: We want to be relaxed, tranquil, we want to be let go. So when you return to awareness after some wandering, the next thing to do is maybe a quick scan of your body to check and see if there are any little tensions you are holding that you can immediately relax. This also points again to a non-grasping, non-resisting frame of mind. We want to simply be.
O is for Open: We want to be open, an open awareness as opposed to a narrow, closed off focus or one-pointedness. We're talking about something other than a pure concentration style, there needs to be a kind of flexibility, a receptivity to anything that comes up on any sense door. This can also point to a kind of space-like three dimensional aspect of openness. Check to see that your awareness is open in this way.
When we're practicing this aware relaxed openness, we're practicing something along the lines of our true nature. Not grasping, not resisting. Surrendered, gone, but aware.
I'll repeat a phrase from one of my old guitar teachers: "practice makes permanent". If your meditation practice consists of 50% spacing out and mind-wandering, to my way of thinking you are creating a mind that will be spacing out and wandering 50% of the time. The mind will adapt to the specific demands that you place on it.
A style such as Mahasi, practiced earnestly, can help us maintain a very high percentage of awareness, and I believe this is a major key to success. But just get that percentage (we can also think of this as continuity or persistence of awareness) as high as you can by any style and any means necessary. While I was getting it done, I used some ancient beeper technology, a device that I could set to vibrate once per minute, that I would hold loosely in my fingers (for maximum effect). So I was meditating in the Mahasi style, noting once per second, and with the beeper device (the motivaider) the longest I could space out would be something less than a minute.
You will space out and wander, that's going to happen. But don't beat yourself up about it. As soon as you are aware, you are aware, you are already back to doing what you are intending to do. In such cases you have unconsciously come back to awareness from wandering. Well done. If anything, simply renew your earnestness and adjust your effort if need be. Balance effort and relaxation.
We practice this so that we can make this our new default. The default mode in a normal modern human is the wandering mind, we need to change this to a relatively persistent aware relaxed openness. We need to train enough to get this state to persist a bit, we need to be able to know that if we take our hands off the steering wheel the car is going to keep going in the same direction, that we're not going to suddenly veer off into thought/attachment. Thought is often graspy - we can't be grasping. You go through the gateless gate with the hands off the steering wheel.
Once the mind is relatively trained to this, the game becomes one of simply stacking the deck with lots of these aware relaxed open moments. For many, retreats are ideal for this, but also some practitioners with a consistent daily practice of around an hour a day have been successful. Daily practice is very important, as it is with any learned skill. Create an intention to get it done, to work on these elements until they become second nature. Back to it, again and again. Keep coming up to the plate and taking swings at the ball. Keep letting go into these moments.
So we have all these little areas in our meditation where we do become aware, relaxed, and open, where we become okay with everything, with every sense door. We lose our self-consciousness, we become pure, natural, and sometimes, maybe even a little bit forgotten. Hands off the steering wheel. And in moments like this, it is possible for something deep down to let go, if only for a moment. Give your unconscious mind permission to let go.
For a longer, more traditional, fundamentalist, repetitive, and mostly morality based instruction (yet then again quite possibly useful if you have the time and inclination to geek out on the old texts), check out "Into the Stream - A Study Guide on the First Stage of Awakening" by Thanissaro Bhikkhu. EDIT: Into the Stream also available in a slightly prettier pdf form.