1) If at all possible, walk into the hospital on your own volition. Resist the urge to enter via the emergency entrance (unless, of course, it is after hours or there is a true emergency/baby is close to birth). Entering unnecessarily through the emergency room screams, well, "This is an emergency!"... even if it isn't. Birth is normal.
2) Bring your own food and drinks (but, by all means, order food to your heart's desire off the menu if you'd like!).
3) Wear your own clothing. Something with "easy access" is nice, but don't worry about anything fancy. Also - Birth washes off. If it didn't, this doula would need a new wardrobe weekly.
4) Use your own water bottle instead of the gigantic ones the hospital provides. "But, I LOVE those huge mugs they have!!" Well, size isn't everything (and you can buy yourself a big 'ole water bottle). If you use your own, you're not labeling yourself (literally) with the hospital's logo.
5) Turn the space into "home" - Think battery-operated candles, your favorite scents, your own pillow, and mood music/tracks for childbirth hypnosis...