If you carry a bag for guide books, maps, brochures, etc., use one with a zipper and hang on to it. Leave your wallet and purse at home. The exception to this is in countries where pensiones and hotels need your passport for an hour or two in order to register you with the local police. If something doesn't go right, smile and be persistent in what you want. Getting mad, yelling or fist pounding will only be met with resistance.
Women have the definite edge here in dealing with men in some countries.
As soon as you arrive someplace, arrange your way on to your next stop. Travel agencies can usually get reservations for you as they book blocks of seats well in advance. When traveling by regular bus, try to get seated close to the front as they will keep packing people in until there is no room left inside. Additional people then hang on the outside and climb on the roof. Always settle on a fare before climbing into an unmetered taxi.