When you're first starting with artificial lighting, one of the biggest things to learn is how different modifiers affect the face. This helpful video compares numerous modifiers of different types and sizes to help you understand their effects and choose what's right for you.
Coming to you from Jay P. Morgan of The Slanted Lens, this video follows him as he mounts various lighting modifiers to a Dynalite Baja A6 Monolight, keeping the front of the modifier a consistent four feet from the subject to ensure that the test isn't affected by the proximity of the modifier, which would make the light softer as it moves closer to the subject. Altogether, the test encompasses three reflectors of varying sizes, two beauty dishes, octaboxes, parabolic umbrellas, softboxes, and large umbrellas.
While there's a lot of conventional wisdom about which modifiers are "best," part of the decision is also your personal preference, so be sure to pay attention to things like highlight-shadow transitions, how the lights affect the background, whether you prefer silver or white lining, highlights, etc. Another thing to consider beyond what the video mentions is catchlight shape. Be sure to think about what shape you prefer, particularly in regards to circular vs. rectangular.
And if you'd like to learn more about the basics of photography, be sure to check out "Photography 101: How to Use Your Digital Camera and Edit Photos in Photoshop."