Planning is key. Sounds backwards but isn't. If you don't plan ahead you don't know how to get around, when things are open, or how much things will cost. Once in Egypt we missed the "last bus of the day" by 10 minutes and had to wait 24 hours by the side of the road for the next bus. Dumb! A little planning and we could have saved 24 hours of sightseeing time. Don't need minute-by-min plan but a general idea, especially of how to get around (train? car? bicycle? when is the next train, and the one after that?) and where you are going to stay. My #1 rule of travel is: always figure out where you're going to stay in advance or at least by morning. If you don't have a place to stay that night you tend to have it on your mind all day, can't enjoy what you're doing. After having spent a few nights on the streets I always have sleeping plans nailed down ASAP for the following night.
The best way to travel cheap is probably to go by bicycle. Actually walking is probably cheaper but it is much, much slower. In Europe you can bike around and stay in campgrounds. Probably overall cost half or one third the cost of typical train and hotel/hostel travel. Plus you might tend to meet more people in campground vs. cooped up in hotel.
I've never done extreme cheap travelling.. except in Egypt. In fact, the top rule of cheap traveling to avoid developed countries. You can live and eat well in Egypt or Thailand or Vietnam for a few dollars a day, room and board. If you really want to see a lot of the world, and new things, I would stick to places like that. Get your vaccines!
Skills for traveling. Rick Steves has a lot of good stuff, but his audience is frugal Lutheran middle-aged types. Also his focus is almost entirely on Europe, an expensive destination no matter what. So you have to take the advice that applies to you and ignore the other stuff. He is not a "shoestring" travel expert, and not an expert on the third world.
Other "rules": always get the best map you can, as soon as you can (Tourist office, usually at train stations); if you're lost, immediately ask for help (in friendly countries, at least); don't be afraid to ask a million questions about anything (like the food you're ordering) -- get good at acting things out, like chicken or fish; use a money belt; carry as little as possible (Rick Steves has a good list).
Travel can be pretty stressful sometimes. I don't know how you do it, but it's nice to have "break" days were you don't have pressure to go, go, go and see, see, see. Also it's best to stay at hotels for at least two nights at a time. Otherwise you only set your backpack down for 8 or 10 hours, which gets to be a drag.
Hmm, I think that's plenty for now. Stick to 3rd world and your money will last. Europe or Japan will cost you at least $50 a day, probably more like $75+ if you use trains and go for the sights.
Asia... I'd get a guidebook for each place you want to go. I guess Lonely Planet has the best coverage. It's worth the $20 or so per country - best purchase you'll ever make. Get the newest copies you can find.
Mostly if you stay "on the beaten track" you shouldn't have too much trouble. For example: If you fly into some main city, and you want to go to some temple, it will probably be in your guide. It will say "buses for the Umbagawa Temple leave from the east side of the city square, about once per hour. Most have a large blue sign.". Mostly if you show up in approximately the correct area, the locals will recognize you as a foreigner and guide you in the right direction, assuming you must be there because you want to get to Umbagawa Temple. Also, this is where it's very useful to know a few words of the local language. Even if you are nowhere near conversant, knowing "please", "thank you", etc, is very useful and pays dividends. So the night before your trek to Umbagawa Temple, learn the local word for Umbagawa, how to pronounce it, and maybe learn the local word for bus. Put the two words together and you will eventually get on the right bus. When you do, if you have even the slightest doubt as to whether it's the correct bus, be sure to ask the driver "Umbagawa Temple?" and open your guidebook and show him a picture of the temple.
Everywhere you go, you will find some English speakers. In places where not much English is spoken, they will often approach you, either to practice their English, because they like foreigners, or just for the novelty of speaking to you. Many people the world over know a few words of English. Once you know a few words of their language you won't have much trouble getting around.
If you're really worried about not being able to communicate some key piece of information, like "I cannot eat chicken", or "I'm allergic to peanuts", then take the time on the plane or in the evening in the hotel/hostel to write it out in local language, by referring to the language section in the back of your guidebook. Even better, most hotel front desk people in touristy hotels will speak some English. Have them write your question/concern in the local language, and you can flash the paper the next day when you need to find the bus or when you're ordering and want to avoid the fried monkey brain.
Finally, a relaxed attitude helps. If you can't find the bus to Umbagawa, don't get too worked up -- maybe explore the town instead, or head into the hills, or whatever. Backup plans are nice, even if just a vague idea. When my plans to rent a car in Fussen, Germany fell through, I was annoyed for about 15 minutes, but then I adjusted by attitude and wandered the lovely little riverside town, following a walking tour outlined in my guidebook. I ended up at a hilltop castle overlooking the city and listened to bells toll as the sun set. It was one of the highlights of my trip.
Lastly, wherever you go you will likely meet a lot of other travelers, especially Germans (they're everywhere) and Americans, Aussies, etc. Hostels are great places to share info in the evening. Whatever they did today can be what you do tomorrow -- except now you're armed with all their tips, how to get there, how much it cost, watch out for the monkeys they will pull your beard and steal all your food.