We evac'd for Katrina. Then I came back and started handling insurance claims. The stories I heard were horrifying.
A few thoughts:
Traffic was horrible. The number of broken down cars... cars out of gas also. Make sure your car is mechanically ready to go. Extra gas is essential. There wasn't a gas station open for 200 miles. After the storm was worse. Gas was being rationed. Being able to jump a curb to get around a stalled car was handy.
Keep the tools accessible. Don't bury them under stuff.
Things fall off other people's trucks. There was a lot of road debris on the way out. After was worse. I went to check out my damaged home after the storm and on the way back to MS I dodged a dresser in the left lane of I59. I ended up scraping the drivers side on a guard rail... another night during the renovations while driving back in a pitch black deserted section there was a black fridge someone dropped in the right lane of I10. That could have killed someone. Slow down. Be careful.
Road food was a good call on my wife's part. Not having to get off the road was nice. It took 10 hours to get from N.O. to Jackson, MS. That's usually at most a 3 hour drive.
Communications: cell phones went down before the storm even hit. During evac I couldn't call my wife in the car in front of me. CB's are a good idea. Next time we're leaving my wife's car though.
Firearms. Keep them handy if you can (some states have some stupid gun laws...). People stranded both on the road and wherever you are going are desperate and might do something stupid. If you bug in law enforcement and medical will not be readily available. Disasters tend to bring out the worst in people. High water tends to bring out critters also. I saw a pig on the interstate on the way back that had to be 450lbs. Snakes and rats were common. Raccoons were out in force. Feral dogs were a problem also.
Unfortunately, the biggest problem with Katrina were the people that weren't prepared for it. They made the rest of us look like fools. When a cat 5 hurricane is coming you leave. Period. The authorities tried to deal with the people that rode out the storm the best they could but they were overwhelmed.
You've all heard the stories (superdome, police, military, deaths, etc.) on the news, all I can say without writing a book is that the real events were worse. Be very sure of your situation before deciding to bug in. Also, be sure the local authorities are going to allow you to bug in. I heard of more than one case where people were forced to leave a safe situation to go to a hellhole of a shelter because the cops were told to enforce an evac order.
PS. One last thing: For 3 weeks, credit cards were worthless. Get some cash before a disaster occurs.