Well first of all you need to decide what you will run with this generator. Stores like Home Depot and Lowe's, etc... have guides on starting and running wattage of the major items used. The guide will show you what size to get. Next you need to decide on what brand to get. I personally recommend a Honda. Now you are not going to get a Honda for $600 but that is something you have to decide. I have two one 600 watts very small and quite and a 3500 watts for running the fridge and larger stuff. One thing to remember is to have something someone can work on. At the start of the Hurricane season this year a lot of folks down here in Florida brought their generators in to be serviced and found out that the repair shops could not get parts for there cheap China generators. You pay for what you get. My 600 watt Honda is over 15 years old and I can get parts for about 30 different places on line or drop it off at any shop around town and have it fixed.
Now that you have your generator you need to use it. Most of the repair problems were because people filled it with gas ran it once and put it away and never looked or thought about it till they needed it. Dumb! Get some STA-BIL fuel additive and mix up the long term storage dosage. I mix all my gas for my law mowers trimmers etc with sta-bil a little preventive precaution goes a long way. Now RUN your generator at least once a month. Just don't start it, plug something into it and make it do it's job make electricity. I run mine once a month while I am cutting the grass (the mowers going anyway) I have a double 500 watt work light and I plug it in and turn it on and work out the generator. I have never have a problem when I take it out of the garage when the power goes out she fires right up on the first pull and purrs like a kitten.
Hope this helps.