Some people like to go casual, some like to dress up, it’s totally up to you both.   Think about your location (a beach? a field?) and work out what would look best in that setting. Bring along something warm in case it gets cold, and spare shoes (in case we’re up a mountain, you can pop your heels on when we get to the top!) I am always available for a quick chat and some advice about what to wear for these sessions.