Well, I see the L.A. area had a 5.1 earthquake and the fears of the "Big One" are resurfacing again now that they discovered another major fault they didn't know about. This was the same after the '94 Northridge Earthquake where a major fault they never knew about strutted its stuff. I was living in L.A. for that one and learned a few things.
1.) Water. The water treatment plant will go down. You need to have plenty of water stocked and water purifying capabilities. Water is Number One on the list. It'll take weeks to repair the water treatment plant and if the aquaduct is damaged, even longer.
2.) Food. Dried food is nice, but it takes water to reconstitute. Canned food is better. Big Lots is the cheapest source for that. Dried beans and rice is not a bad idea, but you need to plan your water to figure on losing quite a bit for cooking.
3.) Cooking. You need a cookstove and fuel. The gas lines will be down and even when they're restored, it will take time to check all the lines in each building.
4.) Medical supplies. Obviously, you need the basics. But if you take a prescription drug, you need to stay up on your refills and not let it drop too low thinking you can swing by the drug store just in time. If an earthquake happens before that, you're hosed. Keep up on your refills the very day you can refill. If possible, try and do a three month supply refill and keep up on it. If you wear glasses, have a spare pair in a hard case in a place you can access it easily. If you wear contacts, have two pairs of glasses both in hard cases.
5.) Self defense. Everyone should know about that. The best self defense is not letting anyone know you have survival resources like water and food. Aside from that, a pistol and shotgun are best.
6.) Shelter. If you home is in rubble, you need a place to shelter in. There will be plenty of things to build a shelter from, but a prefab shed in the yard will usually survive a quake. Something to think about.
7.) A plan. It might be a good idea to leave the area altogether. The roads will be out so this might be a challenge. But if you can, get out. If Hurricane Katrina is a key indicator, the feds will lose control of the situation real quick, if they respond correctly or not. Have a place to go and a way to get there. And if you can get out, get out while you can. Don't wait for the feds if you see the situation starting to deteriorate. Once it does, it will be too late. Also be prepared for martial law if the Big One happens. Once that is enacted, you probably won't be allowed to leave and will be stuck where you are as the situation starts to come unravelled. Not to mention the possibility of being forced to go to a "refugee camp" so they can better house and feed you (which is what they'll say.) Those places will be cesspits, to say the least, and highly dangerous. You do not want to go to a refugee camp or shelter. Look what happened to those that went to the arena shelter during Katrina.
8.) Aftershocks. The earthquake is not over for months afterwards. Aftershocks happen for months after and they can be as strong as the initial quake. This means stay out of damaged buildings. Be prepared for more quakes and act accordingly. If you're trying to get out after the quake, assume every overpass and bridge to be damaged or out and plan routes accordingly. If you must cross over one or under one, do it as quick as possible.
9.) Family. If the quake happens while family members are somewhere else, have a rallying point to meet at. Don't be out looking for them and have them get home to find you're not there and then they go looking for you. Everyone needs to know what to do and where to go if the quake happens.
10.) Sanitation. Improper sanitation is how diseases start and spread. Here's what you need: A shovel and chemicals to put in the pit.