Song Sparrow:
Size: 12-17 cm (5-7 in)
Wingspan: 18-24 cm (7-9 in)
Weight: 12-53 g (0.42-1.87 ounces)
Chest streaked, with spot in center.
Two thick brown stripes on sides of whitish throat (malar stripes).
Long, rounded tail.
Grayish or whitish eyebrow.
Geographically very variable: large and dark in Northwest, pale in Southwest.
Crown dark brown, separated by lighter stripe in center.
Back brown with black streaks.
Underparts whitish.
Rusty tinge on wings.
Flanks and upper chest with dusky background in dark races.
Bill brown.
Eyes dark brown.
Legs and feet dark brown to pinkish brown.
Savannah
Size: 11-15 cm (4-6 in)
Wingspan: 20-22 cm (8-9 in)
Weight: 15-28 g (0.53-0.99 ounces)
Small songbird.
Brown or grayish-brown overall.
Streaking on back, breast, and flanks.
Yellowish eyebrow stripe.
Eyebrow stripe usually yellow, or sometimes beige.
Crown has a pale stripe down the middle, except in saltmarsh populations.
Tail medium-long, notched, and all brown.
A little yellow in bend of wing (inconspicuous).
Bill horn-colored.
Legs pinkish.
Eyes dark brown.
Sorry but I forgot to site my source. Ouch! My above descriptions are from the Cornell University on-line birding guide at
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/
To sum it up a Song doesn't show much, if any yellow and the bill and leg color is duller brown. Also they have the central dot on their breast. You can also go by their song if it is heard. In flight the song's tail isn't notched like the Savannah.