That's tricky - it's not cut and dried anymore - used to be 3 months out on a tuesday was the cheapest time to buy flights but that hasn't been true for many, many years.
The first thing to do is find out which airlines fly out of your airport and if you want non-stop which one is non-stop. Once I have that info then I just start stalking their website to get a feel for their prices. Once I see one I can live with, I book my flight. I've been using Southwest alot more than Delta lately - cheaper flights and not having to pay for luggage fees is great.
I've never heard of skyscanner - I am going to check into that. I'm all for ways to make the flight hunt easier!