"Freeganism is a total boycott of an economic system where the profit motive has eclipsed ethical considerations and where massively complex systems of productions ensure that all the products we buy will have detrimental impacts most of which we may never even consider. Thus, instead of avoiding the purchase of products from one bad company only to support another, we avoid buying anything to the greatest degree we are able"

"Because of our frequent sojourns into the discards our throwaway society, freegans are very aware of and disgusted by the enormous amounts of waste the average US consumer generates and thus choose not to be a part of the problem. So, freegans scrupulously recycle, compost organic matter into topsoil, and repair rather than replace items whenever possible. Anything unusable by us, we redistribute to our friends, at freemarkets, or using internet services like freecycle and craigslist."

Waste Reclamation
Freegan try to avoid being wasteful consumers by refusing to buy food. Instead they practice what is called "urban foraging" more commonly known as dumpster diving. They claim that despite society's stigma's the food recovered is safe and usually in perfect or near-perfect condition"a symptom of a throwaway culture that encourages us to constantly replace our older goods with newer ones, and where retailers plan high-volume product disposal as part of their economic model." In order to make sure that the food is indeed void of bacteria they wash the food in a bleach solution.

Eco-Friendly Transportation
Freegans recognize the negative impact that cars have on the environment. Therefore they choose not to use cars as much as they can. They would rather use trainhopping, hitchhiking, walking, skating, and biking to get around. "Hitchhiking fills up room in a car that would have been unused otherwise and therefore it does not add to the overall consumption of cars and gasoline."
Some freegans are unable to avoid the use of a car completly so they avoid using fossil fuels by converting their engines to use "griesel" or vegetable oil they recover from the used fryer oil from restaurants.

Rent-Free Housing
"Freegans believe that housing is a RIGHT, not a privilege. Just as freegans consider it an atrocity for people to starve while food is thrown away, we are also outraged that people literally freeze to death on the streets while landlords and cities keep buildings boarded up and vacant because they can’t turn a profit on making them available as housing."

Squatters are people who occupy and rehabilitate abandoned, decrepit buildings. Squatters believe that real human needs are more important than abstract notions of private property, and that those who hold deed to buildings but won’t allow people to live in them, even in places where housing is vitally needed, don’t deserve to own those buildings. In addition to living areas, squatters often convert abandoned buildings into community centers with programs including art activities for children, environmental education, meetings of community organizations, and more.

Source: Freegan.info: Strategies for Sustainable Living Beyond Capitalism