A recent article on unexpected.org lists 10 things everyone should know before heading out on a mission trip...
1. Avoid poverty tourism.
2. Don't be an elephant (see article for explanation).
3. Look people in the eye.
4. Ask before taking photos.
5. Take trips that represent an ongoing relationship.
6. Take the time to equip those who are there long-term.
7. Receive the incredible blessings you're offered.
8. Be a story-gatherer and a storyteller.
9. Give yourself. Don't give what they don't need and don't ask for.
10. You are not the saviour of the world.
Be sure to read the whole article here for more detailed tips on how to be prepared for your trip!