Birds

One way is start narrowing identification down by asking yourself, what family of bird does the bird I'm looking at fall into? Is it a large hawk circling over my runway or is it a small song bird on the perimeter fence? Also what are it's prominent colors? How does if fly? What's its behavior? A lot of these details along with good binoculars and good guide can help you. It also takes practice, not unlike learning types of aircraft! 

One thing I did when I first started out (and still do to this day) is use my Nikon not only as binoculars, but the photos allow me to more closely examine the bird on my own terms, long after it has flown past.

You'll notice that you field guide divides the species up by families. So kind of knowing the general characteristics of some of the common families you see in your day-to-day at your airport can greatly cut down the search.