Most people choose a nail shape from a photograph of someone else's hand. The better way is to start from three things you already own: the width of your nail bed, the length of your fingers, and what your hands do all day.
Almond
Tapered sides, soft point. Almond lengthens visually, which makes it the default advice for shorter fingers or wider beds. It is also the most forgiving shape to live with, because the rounded point has no corner to catch.
Square and squoval
A straight free edge keeps lines crisp, which is why French tips and graphic designs are usually cut on it. True square suits long fingers and narrow beds. If the corners annoy you, squoval takes them off and keeps the geometry.
Coffin
Tapered like a stiletto, then cut flat. Coffin needs a little length to read, so it is the shape to pick when you want the manicure to be visible from across the room. Keep it medium if you type for a living.
Oval
Rounded everywhere, closest to the natural nail. If you want people to ask whether you actually went to a salon, oval in a nude finish is the answer.
Every Hands Down set states its shape and length in the name, and each box carries twelve sizes. Start with the shape that matches your week, not your feed.