Breast Color and Streaking - This can often be difficult to use depending on the glimpse. However it is important to start distinguishing between clean breasts, streaking, dots and the differences in colors in those. Remember that streaking can be messy, blotchy, fine or clean. The Colors on the Breast can be tricky as often contrast can be minimal. Finding the contrast can go a long way to
Beak - The key here is to look for the color of the beak and whether or not there is one or two colors. Some sparrows have two colors in their beaks, some have light colored beaks and some have dark colored beaks. Distinguishing the beak colors can help parcel sparrows apart.
Head - With this I am including the eye, even though some separate the two. Learning how to id patterns and color of the head is essential. Chipping Sparrows, White-Throated, White-Crowned, Golden-Crowned Sparrows all have unique heads and one can learn a lot by studying the heads and eyes of sparrows. Of course, Vesper Sparrows are a famous for their eye ring and Clay-Colored Sparrows are also famous for their signature heads.
Tail -Long or Short, White or Dark, can help you distinguish between different kinds of sparrows. Knowing how to look at the tail can be a useful tool to distinguishing between common and uncommon sparrows.
Obviously this isn't a scientific list. This is just the process that I use when I look at Sparrows. If anyone has any suggestions, I'd love to hear
An Immature White-Crowned Sparrow
Savannah and Song Sparrows
Lincoln's Sparrow, a lifer for me!
A Lark Sparrow, another lifer!
Here are some links to Sparrows by AllAboutBirds and Cornell Lab:
2013 Year List: 269