There are some things you can be very sure of but can't do much about. You can tell your loved one it's going to rain, for example, and the most you can do is offer an umbrella. But you can act on your principles. You can even make money from them. You just have to spend some time thinking about them.

For instance, not so long ago, when gas hovered around $4 per gallon in my neighborhood, it seemed that maybe the gas-guzzling SUV era was finally coming to a close. But gas is suddenly much cheaper now, and I've read that SUV sales are likely to trend up again. Clearly, some people think the worst is over. I'm not one of those people. I'm ready to see gas prices surge again. I was thinking, months ago, that I'd be smart to make my next car a hybrid, and I haven't changed my thinking on that.

So what am I feeling fairly confident of? Well, for one, I'm confident that alternative energies are going to become much more important to America in the near future. One promising development is that President-elect Obama seems to agree, as he plans to create millions of jobs "rebuilding our infrastructure, our roads, and our bridges, modernizing our schools, and creating the clean energy infrastructure of the 21st century."

What to do
Given that I'm bullish on green technology and think that environmentally oriented companies are likely to do well in the coming years, how might I invest? Well, there are some interesting possibilities out there, and more are on the way. Since I'm not very familiar with many such companies, I'd do well to consider some green mutual funds or exchange-traded funds. ETFs combine features of individual stocks and index funds. Read all about them and how they offer some valuable advantages over traditional mutual funds. Here are a few for your consideration:

ETF

Focus

Top Holdings Include:

First Trust Global Wind Energy (FAN)

Wind power-focused companies

General Electric (NYSE:GE), BP (NYSE:BP), Siemens AG (NYSE:SI)

Claymore/MAC Global Solar Energy (TAN)

Solar power-focused companies

First Solar (NASDAQ:FSLR), MEMC Electronic Materials (NYSE:WFR), Evergreen Solar (NASDAQ:ESLR)

The Global Environment 60 Index (coming soon, from Claymore)

Five groups of 12 companies in alternative energy, clean technology, sustainable water, green building, and pollution prevention

To be announced

Source: Morningstar.

With those funds and more to choose from, I can easily invest in areas that interest me. So if you're convinced about a future trend, invest in it -- and profit from your foresight.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.