Someone will get sick on the first day in Bolivia. Don't let it be you. Wash your hands a lot. Don't drink the tap water. Don't brush your teeth with the tap water. Don't eat food that you buy on the street. Eat only in restaurants that you know are safe. Don't eat fruit or vegetables that have been washed in tap water.
When we arrive in Cochabamba, you may feel funny at first from the high altitude. It may be hard to sleep the first few nights. You may feel nauseous, especially if you drink alcohol.
You will feel uncomfortable speaking Spanish at first, if it is not your native language. Don't be shy - people have low expectations and will be happy with your attempts. Be polite to people and they will think the world of you. Shake hands with everyone upon joining or leaving a group of people. Say "provecho" or "gracias" when finishing a meal. Little things go a long way.