A typical alpha feedback approach is okay, I suppose, but personally it tends to make me a little drifty, i.e. a lot of the time I was doing that type of feedback I was in trance or daydreaming. I know there are some arguments for feedback without being fully aware, but after getting seriously into meditation, I don't really like the idea of it too much. If you have someone that is naturally more prone to anxiety, really needs some calming down, maybe doing a lot of alpha or alpha-theta, and even drifting off a bit might make some sense. After all, Jim Hardt and Les Fehmi get their results with alpha. But I find it often makes it somewhat more difficult to stay mindful. Who knows, maybe that's a good thing, having to work harder to be more mindful, like exercising a muscle or something. But I'm thinking maybe not.
As far as the stuff I've tried, the only thing I can think of that I would consider taking another look at is a design I came up with that rewards left frontal gamma, and right parietal alpha, like this:
- F3 Gamma (37-43) up
- P4 Alpha (8-11) up
- P4 Beta (15-25) down
So you're rewarding Gamma around one of the sites that Davidson's research suggests, and you're in line with basic symmetries, i.e. you're rewarding fast wave on the left frontal and then slow wave on the right parietal, so maybe that's something to look at. Rewarding the left frontal Gamma seems to help keep me more present. But like I say, these days I'd just as soon meditate.
The trick with the Gamma is that it is really easy for movement/artifact to give false readings there, but there are some things you can do. Requiring that a short moving average (500ms) of Gamma increases, as opposed to the raw amplitude, seems to help quite a bit.
For meditation, whatever the approach, the goal is to be continuously aware of the here and now. My favorite for that would be Mahasi style vipassana. A good intro might be the Practical Meditation Instructions ("Mahasi Lecture") mp3 found on a Vipassana Hawaii webpage. It's just some old Mahasi stuff read aloud, but I'd recommend it.