To clarify this a bit, I'd like to take a leaf from the book of Taoism to describe my approach to this form of living. I am by no means an expert, but Taoism, from my reading and experience, suggests a life in which one remains "receptively passive" to the movement or flow of life, and when one acts, it is in accordance with the flow of one's life, and is thus effortless. When one fights against the flow, one finds difficulty, suffering, unhappiness, etc.
Let me put it in terms of relationships. To live in the ever-present now, one would exist in a way that is most calm and harmonious to one's nature and the nature of others. That does not mean never disagreeing. If, for instance, one's partner is a creep, it may seem more harmonious to shut up about it and take it--whether it be abuse, derision, abandonment, etc. However, it is damaging to oneself, and doesn't go with one's personal needs. Resentment and anger will build until you can't take it anymore, and then the flow of need will cause you to act out eventually.
Living in the moment, in this case, means not resisting the urge to speak up. Resisting the urge is hard, and it hurts the current moment. Instead, one should speak up and say, directly, "When you say this/do this/etc. I feel hurt and ashamed." At the same time, it does not mean bringing up all sorts of past hurts--those are past, and the reason one might be bringing them up is because one has held onto them instead of expressing them when they occur. It's the same with positive elements. When one is happy, one should express so, and share the joy of one's life with others. If another's actions hurt one's flow, by all means one should act to change that flow, even it means leaving. The release I've heard described from this kind of action (leaving a creep) is caused because a major obstruction has been removed.
In terms of money, living in the moment does not mean racking up credit card balances so that one can go on a vacation "now," without consideration for the future debt or insolvency. In fact, I would contend that purchases on credit are actually living in the future, and not the present, for one's subconscious reasoning is that a larger TV, a new dining room set, or a McMansion will make one happier, and it suggests that one is dissatisfied with one's life as it is. Living within one's means is one way of existing within the flow of one's life. Seeking to purchase items one cannot yet afford goes against one's flow. Buying a house and having payments one cannot afford is a gaping example of this, and it does not increase one's happiness (as many thousands of homeowners will attest to).
Even in terms of food and exercise, living in the moment means paying attention to right now--not one's future goals, but one's eating right at this moment. If I truly live in the now, I eat only when I'm hungry--and I enjoy every tasty morsel of food while I eat it, not working on the computer or watching television while I do it, but savoring everything. It means enjoying my activity--whether walking with a friend or doing zumba or bellydancing--and it means living in that moment happily, without constantly looking in the mirror or stepping on the scale to see whether it's doing any good. If I am only living in the future ("I want to lose 10 pounds") or living in the past ("I don't ever want to be that fat again") I will not be happy now.
And now is what counts. Past is past, future is future. We can't live in either one. I don't write because I want to get published some day. I write because I love it, and when I do it, I am happy.
Thoughts? Bones of contention?