You need to try and get the professional look without looking dowdy. Smart suit in a darkish colour, can be a trouser or skirt suit. Nice blouse, not too bright but can be coloured. Sensible shoes - you can wear heels but not too high or too strappy. If you have long hair it's probably best to tie it up. If you're going to wear makeup, make it light, daytime makeup, not as if you were going clubbing.
TB