A lot of the cheapest accommodation options don’t have websites. Sometimes just showing up in places and having a look around gets you a cheaper bed.
Camping is an option, bring a hammock instead of a tent.
Don’t book hostels online, all these websites take commission (making your bed cost more). Find the hostel´s number and call them directly. If no phone, check online if there is availability, and if there is just show up.
Get skype credit instead of local telephone chips. Most hostels have good wifi, this enables you to make very cheap calls to local places everywhere.
Eat where the locals are eating.
Eat in markets and on the street; some of the cheapest food we have found has been here.
Stay in hostels that have a kitchen. Making at least one meal a day really brings food costs down.
Careful using your card to pay in shops and hostels. Sometimes they put charges over and above their bank (as well as your own)
Avoid ATM machines and take money out at casinos. Faf around at the black jack table and LEAVE! Casinos don’t charge you to take out money, so only get charged your banks fees for the transaction.
Take local transport, at times a bit hectic but pretty good fun.
Taxis are cheaper if hailed from the street compared to the ones waiting outside the establishment for you. E.g Dont get an aiport taxi, walk to the street and flag one down.
Hitchhiking is the cheapest form of transport but just hope to encounter decent human beings.
Travelling with friends brings costs down compared to travelling alone. Sharing food,taxis, beds cheaper!
Volunteering can be great fun and keeps costs down. Check WOOFing for good farm projects. Check ARCAS in Guatemala for great volunteering projects with animals.