One that's somewhat oversized is good. You want the kind with a split back and leaf springs hinged with a pin at the center, not with spring clips all around the perimeter. The latter type don't give even pressure in the center, in my experience. There is a frame made by Premier that is usually orange--avoid that one. The construction is a bit light. My favorite print frame is a frame sold by Kodak for dye transfer printing--very sturdy with anti-reflective glass. Old frames made by Century, Korona, Grundlach, and such are often good frames, but sometimes the corners may need to be reglued.

Anti-Newton or anti-reflective glass are ideal. Whether you actually need it will depend on your film usually. If the film base has a retouching surface, which is often the case with sheet film, you may not need A-N or AR glass.