A venue that enforces this dress code is intent on creating a dining experience that is a few steps above one that you would have at a casual restaurant chain. The idea behind business casual is that you want to look good in case you run into the head of the company, but the style is relaxed.
Accessories
Keep accessories to a minimum. Men should wear a few quality pieces, like a nice watch and a ring. Women can add a necklace and subtle earrings as well.
Sport Coats
Sport coats for men are optional. It never hurts to bring one if the meal is a business meeting instead of a casual lunch. Skip the tie, though.
Khaki Pants
Both genders can wear pressed khaki pants. They are stylish enough for the office but still casual.
Dresses
If a woman wears a dress, she should pick one that would be appropriate for attending religious services or working in an office. A skirt that covers her knees when she's standing and a nice blouse will also suffice.
Shoes
Women should choose dress shoes that don't have too high of a heel. Men also need to wear nice, polished footwear--no athletic shoes.
Grooming
All clothing should be clean, ironed if necessary and of good quality. A man's facial hair should be clipped to a short length. Women should use makeup and scents sparingly.