In decreasing order of expense: Hostels, campsites, couches.
- Hostels usually range from $10 - $25 and are the friend of backpackers and budget travelers everywhere, especially if they have hot showers, laundry, a kitchen, and wifi.
- If the weather is right, camping can be even cheaper - many campsites are $5 - $10 per night. Look for ones with on-site hot showers and laundry. Bring a light tent you can carry, and you can sometimes even pitch it in a park for lack of other options.
- Go to Couchsurfing.org and sign yourself up. Take the obvious precautions - verifications aren't as important as you might suppose, but references are vital and choosing a host of the same age group and gender is suggested - and you could stay for free in every city you stop at.
- For more long-term stays, you could even look into housesitting.
Do a good amount of research into what methods of transportation are cheapest. Some countries have hideously expensive public transport, while others do not. Also remember to calculate in the number of people traveling with you.
- Look into rail passes (BritRail, Eurail, JR Pass, Seishun Juuhachi Kippu) for the cheapest deals.
- Taxis are really not a thing you should be doing. Check prices just in case - and remember they will go down per person if you are traveling with a group - but do your best to avoid them, especially from airports. Take a train or bus instead.
- The same deal goes for bus passes, and full-day tickets.
- Renting a car might be cheaper than you expect, especially on islands or in countryside locations. Southern Japan and Langkawi rent cars for around $30 - $60/24 hours, which is very cheap indeed when split between five friends.
- If you need to fly, first do a search for local budget airlines, such as AirAsia (self-explanitory), JetStar, RyanAir (Ireland) or even tiny companies such as Peach Aviation (for domestic flights in Japan). You might be in for a slightly less luxurious ride, but it's worth it.
- Hitchhiking is not recommended, especially for young women traveling alone. (This is absolute balls, but it is also something to be rightfully cautious about.) If you are planning to attempt this, bring your cell phone, a knife, a dog, a friend, a flamethrower, and at least three bazookas.
Food is another place you can save money.
- Don't eat at restaurants, unless you feel like splurging.
- Cook and pack a lunch, if you're staying somewhere where that is possible.
- Bring snacks for the road - energy bars are expensive, but nuts, fruit, and dried goods may not be. That said, if you can spare money for energy bars, they can be very, very helpful.
- Shop at grocery stores and convenience stores. Many of them sell cheap sandwiches, and have microwaves or free hot water - if you need to live off cup noodles for a while, that's okay.
- But more importantly, shop for what is cheap, basic, filling, and high in protein. A shitton of candy will do absolutely nothing to help your long-term energy level, strength, and health.
If you're touring historic landmarks or local attractions:
- Try to find things with free entry.
- Also look for locations that you will be perfectly happy visiting the outside of, rather than dropping $25 (that could be going toward food) on a tour of some reconstructed and unauthentic interior. Plenty of castles, statues, parks, and city attractions are more fun to experience by exploring, picnicking, or climbing around the outside.
Know what you're doing with your money.
- Make a budget.
- Do it before you leave by calculating every single thing on your itinerary, plus food, accommodation, entry fees, transportation fees, and everything else. Figure out how much money you can spend each day.
- Keep track of every single thing you buy, and keep an up-to-date ledger with how much money you still have. When in doubt, always overestimate what you spent.