As you may have figured, there are many different kinds of zombie outbreaks, depending on the amount of zombies, the type of terrain, etc. Here, I will try to help you understand the differences and what you can do to survive them all.
"Class 1
This is a low-level outbreak, usually in a Third World country of First World rural area. The number of Zombies in this class of outbreak ranges between one and twenty. Total human casualties (including those infected) range from one to fifty. The total duration, from the first case to the last (known), will range between twenty-four hours and fourteen days. The infested area will be small, no larger than a twenty mile radius. In many cases, natural boundaries will determine its limits. Response will be light, either exclusively civilian or with some additional help from local law enforcement. Media coverage will be light, if present at all. If media is present, look for common stories like homocides or "accidents", This is the most common type of outbreak and also the easiest to go unnoticed.
Class 2
Urban or densely populated rural areas are included in this level of outbreak. Total zombies will range between twenty and one hundred. Total human casualties may reach as high as several hundred. The duration of a Class 2 outbreak may last no longer than a Class 1 outbreak. In some cases, the larger number of zombies will spark a more immediate response. A rural, sparsely populated outbreak may extend to a hundred-mile radiu, while an urban outbreak may encompass only several blocks. Suppression will almost certainly be organized. Bands of civilians will be replaced by local, state, even federal law enforcement. Look for an additional, if low-level, military response, the National Guard in the United States or its equivalent abroad. Most often, so as to ease panic, these units will take a more noncombatant role, providing medical assistance, crowd control, and logistical support. Class 2 outbreaks almost always attract the press. Unless the attack occurs in a truly isolated area of the world, or one where media is strictly controlled, the story will be reported. This does not mean, however, that it will be reported accurately.
Class 3
A true crisis. Class 3 outbreaks, more than any other, demonstrate the clear threat posed by the living dead. Zombies will number in the thousands, encompassing an area of several hundred miles. The duration of the attack and a possible lengthy mop-up process could last as long as several months. There will be no chance for a press blackout or cover-up. Even without media attention, the sheer magnitude of the attack will leave too many eyewitnesses. This is a full blown battle, with law enforcement replaced by units of the regular military. A state of emergency will be declared for the infested zone, as well as neighboring areas. Expect martial law, restricted travel, rationed supplies, federalized services, and strictly monitored communication. All these measures, however, will take time to implement. The initial phase will be one of chaos as those in power come to grips with the crisis. Riots, looting, and widespread panic will add to their dificulties, further delaying an effective response. While this is happening, those living within the infested area will be at the mercy of the undead. Isolated, abandoned, and surrounded by ghouls, they will have only themselves to depend on.
Class 4
(Living in an undead world, Coming Soon)"
-The Zombie Survival Guide, Max Brooks