What is the Sunnah of clipping finger nails for hands and feet? Also how often should one clip their nails?

Cutting of the nails is Sunnat. The Mustahabb method is to start from the right index finger to the right small finger then the right thumb. Thereafter, the left hand from the small finger to the thumb. Cutting of the toe nails will be from the small left toe to the small right toe.

Cutting of the nails should not be left for more than 40 nights although it is preferable to cut them once a week. (Mirqaat vol.2 pg.45)

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai