In most cases you can't run your air conditioner on it. Terms like amps and horsepower are meaningless to most people. Ask the dealer specifically how many watts the generator will put out and for how long and how big a load it can handle. A television uses 300 watts, a freezer 330, a water heater 3,000. Compare brands and models.
Dealers can provide manufacturers' toll-free numbers for technical questions.
Make sure you have the right cords and connectors. You don't want your generator sitting useless. An auxiliary fuel tank is a good idea. Most starters use rope pulls, but if yours uses a battery, make sure it's kept charged. The time to buy is not after the storm.