There's a superstition that you can't kiss till the third date! If you do it earlier, you loose the affection and desire to have serious relationships. You feel that a person is easy to kiss and have affairs. But if you kiss on the third date, you feel that it's not so easy to get this date and ability to kiss!
So what is allowed on third date? I think, it's very subjective and individual. In general, you can ask more private questions, you can still talk about general topics and interests. You can go to some romantic place to show that you are not just friends and people who like to have fun together. You can bring a small surprise (if you haven't before) and show your attraction.
Third date shows a lot, a woman can allow to kiss her, a man shows that he is ready to meet a woman more and more times.
The first date is a date of evaluation. The second one is to feel how comforable you feel next to your future spouse. The third one is for romance.
So pick a good restaurant, last seats in cinema, put candles on the table and switch on pleasant music. You can massage shoulders, kiss cheeks, hold hands.
Or you can go to the beach and swim together - and if you feel cold in water, you can hug and kiss! Mmm...
I hope that post was useful for you!