I often hear people say that having a birth plan isn't a good idea - "it leads to disappointment" or "birth can't be planned". This is why you need:
PLAN B
Plan A = ideal. Plan B = back up.
Considerations:
1) Common or likely pregnancy & birth complications?
2) What do you need to consider if these pop up at some point?
3) RESEARCH
4) Educate your support people
5) Discuss with care provider as necessary
6) Re-evaluate plans based on your HEALTH and your baby's HEALTH

A planning session with your doula shouldn't require butcher's paper up on the wall! Image courtesy of Wikimedia Commons.
The benefit of Plan B lies in the research and preparation. Research widely.
Further reading:
Informed Birth Preparation
Categories
#Quick Tips for an Awesome Pregnancy and Birth