This plan is good for outbreaks up to level 3, but not level 4.

Upon hearing of strange attacks, murders, disappearances or other dodgy events that might indicate a zombie outbreak, I will initiate stage 1. This is the stage where I take stock of food supplies and weaponry which I have pre-prepared and purchase more to fill the holes. I will then monitor the news closely keeping watch for further developments and anything suspicious to indicate that the situation has been contained, but the government is covering it up.
If the zombies existence is reported on the news and through other forms of media, I will initiate stage 2. That is, prepare for a zombie attack on my house within 24 hours. I will take all food and supplies and weaponry upstairs, bring in a ladder for access to the upstairs area, and destroy the stairs. I will then fill the process of transporting the water (by bucket) in our water tanks upstairs to the upstairs area whilst someone from my family patrols the perimeter. When as much water as can be stored in various containers has been transported upstairs. I will then begin taking board games, and other things that can be used for entertainment upstairs.
All this time, someone will be monitoring the zombie situation and keeping others up to date on the spread and symptoms.
I will then proceed to wait on the roof, keeping a look out for zombies and rescue teams.