Right Concentration is a big topic of discussion amongst many teachers in Theravadin Buddhism, in particular, and other teachers in other traditions. As to the scriptures, going back to the word "right," Samma Samadhi is the phrase they use for Right Concentration. It has its own definition, but the definition that is normally given conflicts with the definition that is given in other places. So this is a point of confusion that we have to accept, being two and a half thousand years late (or maybe a little early for the next one!).
Concentration can be in general of two types. One is that our minds are one-pointed. Stare at a flower and keep that image in your mind, only that image, this is one-pointed. Another type of concentration moves, you reflect on how fortunate you are, you can get concentrated, but it is a type of moving concentration. The type of concentration that Vipassana meditation wants to develop is a moment to moment type, which can use both basically. It can be one-pointed at times, but it is not so important compared to every moment, when life is changing, because that is going to develop more Wisdom.
The one-pointed concentration is called in Pali "Samata." Samadhi includes both. And this was an interesting point that even Rosemary and I did not understand for the first few years of our practice. We thought that Samadhi and Samata were the same thing, that they both meant one-pointed concentration. But Samadhi means both the one-pointed Samata, and it also includes Vipassana. Samadhi is really our overall practice, being mindful, being concentrated each moment is what we would like to develop. So this is an interesting thing to consider. If you get very concentrated one-pointedness, say on a flower, a mantra or other things, that is fine for sharpening that bit of concentration, but it doesn't mean you are going to have wisdom.
I refer to that in the last evening's talk of the regular retreat. When you get concentrated in a one-pointed way, you can feel a bit of peacefulness, you can forget the world, forget your Dukkha and everything else, but as soon as the concentration is over, everything is still there, it is still there.
So one-pointed concentration works on suppressing everything else, keeping it away for the certain amount of time that we are concentrated. Whereas the concentration working within Vipassana sees things for what they are. In general you could say that what we're doing as far as concentration is letting go of the obstacles.
When we say the word "hindrance," we use the phrase "Five Hindrances," they are termed opposites to concentration. So here we spend our time largely on letting go of hindrances, figuring out every way to let go of them. If we let go of the hindrances, what will happen to the concentration? Automatically it can come by itself, it's like a see-saw effect. If you have got a lot of hindrances, your concentration is not going to do anything. Some people will suppress them for a while, for the one-pointedness, but as soon as they let go of the one-pointedness, the hindrances come back. So we are working on letting go of the Five Hindrances, bit by bit, bit by bit.
As to how it supports the other seven factors of the Noble Eightfold Path - how can we think Right Thoughts unless we can concentrate? How can we have Right Speech unless we can concentrate? How can we decide for ourselves what is good Livelihood unless we can concentrate? So in that way concentration is part of all the other aspects. In a similar manner you can relate back the other way. How can you get good concentration if your speech is lousy, your Morality is lousy, and you have got wrong view? Then the concentration you get might be one-pointed, but you will not get the wisdom type concentration because the other factors are not supporting your concentration either. So in this way concentration supports the other seven, and the other seven support the type of concentration we would like to get.