The only real way to do this effectively is to find ways to make people see that it is in their interest to conserve the environment. It would be nice if people would do things because they are the right thing to do, but it is not very realistic.
So, if you want people to practice conservation, you must point out to them how conservation will benefit them. Perhaps it will benefit them by giving them nice places to go on vacation. Or perhaps by allowing them clean rivers to use for boating or swimming. But one way or the other, you have to show how it is in their self-interest to conserve.
Well, the obvious answer is through education and media/propaganda. With respect to education, environmentalism needs to be a bigger part of education from elementary school on up; maybe a strategy would be to not limit it to science as that makes it only applicable or interesting to those students interested in science. Environmentalism should also be a part of history and social science classes: i.e. sociology and economics.
The other way to promote conservation is simply by talking about it in everyday life, blogs, writing articles, writing books, television programming weblogs and writing to politicians or electing politicians who are acutely aware of the benefits and necessities of environmental conservation. In general, because it is an issue that affects all life, it should not be limited to discussions among ecologists and scientists. It has become such a necessary part of life that its implementation needs to be concerned in all aspects: that’s why it makes sense to say that recycling is a practical and economic issue in terms of saving resources but also a moral one in that future generations will benefit from this. Thinking more of future generations is altruistic and makes sense to integrate environmentally conscious ideas with religious tenets. That’s just one example: talking about environmental conservation in church may seem odd, but the point is that practicing environmental conservation has ethical implications so it makes complete sense. It also has political, economic, historical, and in certain situations like art installations and political activism, it can be a source of artistic expression. Promoting a cause = talking about it everywhere; not just in limited contexts.