Planning a trip to Bolivia is often used to fulfil a dream. It's a dream about discovering a typical and authentic Latin America, about being in the middle of mythical landscapes, and about meeting people with a unique culture. So that your trip to this destination is magical from the beginning to the end, you should pay a great deal of attention to what you put in your suitcase.
The image you probably have of Bolivia is one of a country at altitude where it gets very cold. You're not completely wrong but it all depends on the season. You should therefore plan your clothing accordingly bearing in mind that temperatures can fluctuate between 20° and -30° at 3000 metres in the Altiplano. Don't panic if you forget something, Bolivia is renowned for its markets. There you'll find everything you need to equip yourself and to help you best cope with the Andean climate. You also have to think beyond stereotypes when your preparing your trip. Bolivia is not just cold and at altitude. If you visit the Amazon in the north of the country, be prepared to endure temperatures flirting around 40°. Again, you'll need to plan your wardrobe accordingly. Ditto if you intend to go on a mountain trek, make sure you pack the necessary equipment. Again, it doesn't matter if you forget something, you'll always be able to find whatever you need out there.
Preparing your first-aid kit must be done with great care and meticulousness. Bolivia is not known for its impeccable hygiene conditions. Digestive problems are common among travellers. Take something to alleviate them. Another frequent problem is acute mountain sickness. When you arrive in La Paz, you're already 4,000 metres above sea level. It's also important to remember treatments for malaria if you plan on visiting the Amazon.
Finally, and this is valid for any trip in the world, you should carry a camera with you to capture your memories, a debit card for withdrawing money, your international driving licence if you plan on driving and a photocopy of your passport in case you lose the original.