What to wear...
Wear what makes you comfortable.
Don’t forget to ask yourself, “when I find these pictures in a photo album, how are they going to look?” Something that is very “in” now may look silly in 20 years. Ever watch a movie and guess when it was filmed by the clothes the actors were wearing? Remember parachute pants? Bell bottom jeans? If your pictures are to be used in the here and now (like commercial head shots), then dress trendy. Otherwise I would recommend something a little more timeless….
Try to avoid patterns and labels, they distract from the main subject…you! Given the choice between a patterned shirt and a plain one, I would recommend the plain one. In general, simpler is better. When coordinating pants and shirts or skirts and shirts, try to pick colors and fabrics that contrast, particularly with dark colors. If you wear all dark colors of the same material, it will be hard to distinguish any details in the picture, making it boring.