As Abdul mentioned - light is important. Side light sculps your head, all curves become visible and noticable, unfortunately also any skin defects, but in normal eye-to-eye contact they're hardly noticable, its pictures where they come out.
Avoid bottom light. Put a flashlight under your face in front of a mirror and you will see why
Second thing - viewing angle. Being on eye level with a person you're speaking to is best. If you are taller, then make sure you take care of you're facial hair and skin on your neck.
Some people mentioned problem that they look different on pictures and in mirror. It's completely normal. Human face isn't symmetrical. Mirror "flips" your face so it looks different then in nature. You just have to get used to it.
Talking about poses... Their not important as long as your body language is ok. More important part is facial expression. Practice in front of the mirror various type of expressions and try to learn best ones.
I'm a photographer, so if you've got any further questions feel free to PM me. Or ask in this thread and I'll try to answer.