Men do not have a choice about whether to wear a jacket: the host at a "jacket required" establishment can and almost certainly will deny entry to guests sporting only their shirtsleeves.
For the ladies
Like "jacket preferred", consider the "jacket required" dress code a license to add some fun and femininity to a business casual ensemble. Skirts and dresses are absolutely welcome, as are heels. But keep your shoes somewhat modest -- no venue that demands such decorum from its male patrons wants its female clientele teetering around the
room on five-inch open-toed heels covered in hardware. Understated elegance is the goal.
For the guys
"Jacket required" venues may be more likely to have loaners available, but remember again that you will have no control over the look, feel, or smell of the jacket you borrow. And you'll have only yourself to blame if you accidentally dip one of those too-long sleeves in your soup or drive your date to the farthest corner of the table with the enticing smell of mothballs. Better to save yourself the trouble and invest in a blazer or sport coat, which
you can pair with a smart button-down and dress slacks, khakis, or chinos. Dress shoes or loafers, with black or grey calf-length dress socks, are a must.