Before I book my international flights, I often set up an alert for airfares on a couple of different sites. For instance, if I know I’ll be going to France in May, I sign up for an alert from my home airport to Charles De Gaulle in Paris. That way I have an idea of what fares are if I purchased them right now. Plus, I receive alerts when the fares go up or down. Usually these alerts come once a week.
One site I use is www.kayak.com and another is www.airfarewatchdog.com. There are others but these two will give you a good feel for what you will pay. You can either book from them or go directly to the airline once the fare is in your budget.
Plus, kayak will also show you where you can fly on your budget. List your home airport and how much you want to spend…they show a map with places you can go for that amount.
Another helpful tool is to know what airlines charge for additional services. Check out www.smarttravel.com for their downloadable chart of airline fees. It might come in handy.