First: I’m cheap as hell. My job gives me an amount of free time comparable to a medical intern, only with somewhat less pay. I try as hard as possible to avoid spending what I do make, even to the point of volunteering to be DD more often than necessary because I can’t buy drinks when I drive and people buy them for me when I’m not. I save like a miser, and this is critical. I have a bunch of sub-$3 meals that I make for myself (baked potatoes with butter and salt are almost free!) and I never eat out except on social occasions. In my experience, peoples’ food budgets are one of the most flexible areas there are.
Second: I’m entirely willing to sponge on friends. On my last two trips (France and Ecuador) I managed to spend damn near nothing beyond airfare, by getting a free place to park a car near the airport, lots of free housing at friends’ and friends’-of-friends houses, and splitting transport costs with the friends I traveled with. There’s no shame in this, doubly so if you do the same for your friends when they come by where you are. Are you Couch Surfing? It’s free by design, although it might be less available if you’ve got kids.
Third: Look for cheap alternatives to the normal ways that people soak travelers: housing, food, travel, and admission to tourist attractions. Are you eating in restaurants when you’re traveling? Don’t; they’re way expensive. Are you staying in hotels? If you’re traveling in summer, don’t; campgrounds are much cheaper, especially in national parks, and you’re not traveling to experience hotels, right? Once again, this goes double when you’re talking about a stopover between drive days. Are you going anywhere at the seasonal peak? Why? It’s cheaper to go offseason. Airfare to France cost me less than half as much to go in February than in the July-August peak. Are there cheap or free tourist attractions? National parks are great, as are Smithsonian museums, factory tours, and other things that you pay for with your tax dollars or by virtue of their being advertisements.
Fourth: Find ways to save money. Anything with a regular monthly payment is suspect, because it’s money taken painlessly and silently out of your paycheck. You may need internet, consider canceling your cable television, your Netflix, or your wired phone line. Get a cheaper place to live; I lived in a dark basement for a year to fund a couple of trips. I haven’t bought a shirt from anywhere but Goodwill since college (possibly high school, I’m not sure.) Buy food in bulk, and pay careful attention to unit prices at the grocery store ($ per ounce, pound, and gallon). Find a way to do dates with significant others for free or cheap-- picnics, hikes, movies at home, inexpensive events (I like swing dance nights, and they all seem to be $8 for four hours of ballroom time), and candlelight dinners at home. People spend a lot of money trying to impress significant others, and I find this not worthwhile.