Tip for beginning string players
Keep your fingernails carefully sculpted and free of nicks. The nails on your noting hand should be kept very short, as close to the "quick" as you can get without causing pain. After so many years, the finger tips of my noting hand extend a full eight inch past the ends of my finger nails. This is necessary so your finger nail can't contact the fingerboard first and prevent the tip of your from properly engaging the string. Of course you want to be sure you can still execute a pull-off easily and accurately.
The nails of the picking hand will be shapped differently for various instruments and styles. I cut my thumb nail all the way down because I use a thumbpick when playing finger style. My little finger likewise has its nail cliped down as far as it can go since I don't ever use it to pluck strings. The nail of my index finger is cut and filed smooth to match the contour of my finger tip. I treat the second and third fingers similarily to the first since I sometime use them to pluck strings while holding a flatpick. Perhaps the nail of the ring finger doesn't extend out quite as far as the finger tip.
If I remember to do it, I'll leave a little squarish corner of the nail of my middle finger, on the thumb side of the nail. This little protrusion, properly shapped, can be helpful when playing banjo clawhammer style.
Merle Travis and, I believe, Chet Atkins left their nails somewhat longer than I do but mine aren't strong enough to be kept too long. The idea, though, is to use the pad of your finger when actually pulling the string sideways for a note but let your nail be the last thing that actually touches the string during release.
You'll need lots of experimentation to get this worked out just right for you. With luck, lots of folks who have already worked this out for themselves will come in and share their finger nail tips.