Dress for your best client, choose solid colours when possible, and avoid white shirts. A dark jacket over a bright colour adds a nice slimming band of colour that is very flattering. Select fitted styles that are not baggy or tight.
For makeup, concentrate on evening your skin tone, and apply it as you would for an evening out. Photography lighting can be bright and wash out natural skin. If you tell your makeup artist that you are having professional photography done, they should know what to do.