How do I cover interior dry wall sharp corners?

They make vinyl corner trim with a bullnose edge, but you would have to nail them and then skim coat the flanges with joint compound to blend into your drywall. http://www.homedepot.com/p/Phillips-Manufacturing-Company-8-ft-x-3-4-in-Vinyl-Bullnose-Corner-Beads-35-Pack-BN3VYL/202035413?cm_mmc=Shopping%7cTHD%7cG%7c0%7cG-BASE-PLA-D22-BuildingMaterials%7c&gclid=Cj0KCQjw78vLBRCZARIsACr4cxwwfiN7v8zomtM15N7XgyHpXqzQ9cpsyh6gYW92liq3lmSBIXnMl7UaAqlqEALw_wcB&gclsrc=aw.ds

If you just want to prevent damage you can just tack in clear plastic corner guards ... http://www.homedepot.com/p/Trimaco-1-1-8-in-x-1-1-8-in-x-8-ft-Plastic-Corner-Guard-Commercial-01188G/100119073

Use corner guards that are rounded

There are curved clear plastic strips that are sometimes self-stick that you can usually buy at Hardware stores where wall building supplies are bought. I bought some so no-one would bump into sharp corners.

Re: the comment above about using the bullnose edge drywall strips

These are NOT nailed down. You will unlikely get them to stay down and the nail holes will eventually show through. They are installed directly onto raw (unfinished) drywall edges with drywall mud (paste). The key to getting them to stay on the corner is to cut one side of the drywall slightly less wide than the other side. This allows the strip to "roll over" around the edge and stay adhered.

To achieve a finished look to the corner of your walls, the process of installation does require experience, the correct tools, and patience. It is not for the inexperience diy -er.

The clean plastic strips are generally used on a wall corner where two walls covered with wallpaper meet, as a guard against the wallpaper peeling. The stickiness on the backing varies in quality and how long it holds to the wallpaper varies from brand to brand, and also how straight the corner of the wall is.