Well that depends on what you are prepping for. Personally, I am not worried much about an EMP (natural or man-made) so I don't do any prepping in that area. I focus my attention towards Beans, Bullets, and Band-aids (food, weapons, and medical supplies). Right now I am mainly working on food and then medical supplies. There aren't many bullets out there for my weapons (mainly for two reasons ... the Department of Homeland Security buying millions/billions of rounds and people's fear that something is going to happen is causing them to buy up what ever makes it to the shelves).
As far as food... I store what I eat and eat what I store. I started off just storing rice and beans... it was cheap and I could get a lot of it. Now I'm storing more varieties of food. I just make sure that it has a good shelf life and that it is stored properly. I look at my food storage as a large pantry. I am now going to get some quick prep food (Freeze-dried and dehydrated food) so we can have some quick meals should we need them.
For my Medical supplies... I started off with a first aid kit and I am slowly building it up. I am including not just supplies but also training. On my way to church a couple of weeks ago a wreck happened right in front of me. Thanks to my limited training (CPR, First Aid... and the stuff I learned in the Army) I was able to quickly assess the situation and get one woman out of a car that was smoking even though she was hurt (I was concerned her car was going to catch fire)... I moved her to my car and had her sit down. I turned off her car... then I quickly assessed her injuries then checked the other woman... she couldn't be moved so told her to stay there ... I told both women that everything was going to be alright and help was on the way. What was nice, was that I knew that I was doing the right thing.
If you are truly concerned about zombies (which I wonder if you really are)... then you might consider buying a good aluminum bat, machete, cross-bow, and chainmail to keep zombie teeth from making contact with your fleshy parts.