Figure out how much you'll need
Start your budget with the biggest expenses first – usually this will be your flights, but accommodation also adds up. In Lonely Planet's The Big Trip we included sample prices as a rough idea of how much it costs for a room, a street snack or a restaurant meal. In the destination pages of lonelyplanet.com - eg lonelyplanet.com/china - there is often specific information on a country's costs under the 'practical information' section.