kitten in heat

Can someone please tell me the classic signs of a kitten in heat. My kitten is just over 5 months and for the last day or so has been doing quite a bit of rolling around on the floor which she hasn't really done before. Thanks

Floor rolling is not a classic sign of heat, although I am not dismissing it.
   
Typically females coming into heat may become unusually affectionate, rub their hind quarters against furniture, stuffed animals or humans, spend excessive time licking the genitals and vocalize loudly ('calling,' and it will go on until she actually mates).
   
She will assume the mating position; head down, front legs bent, rear up in the air, tail raised and off to the side for easier access for the male and her legs will tread as if she is walking in place.
   
She may also spray with a fluid that smells very strong. The tail may quiver and she may do the walking in place as she sprays.
   
If she doe not mate she will go into heat as much as every three to four weeks for months at a time until she either gets laid or spayed.
   
Typically cats can be spayed at six months so you are in the home stretch.

NOTE: This is an observation:
   
A cat does not necessarily go into heat every month.
   
I have 3 9-month-old females at home right now.
   
Amelia went into heat at 3 months & 3 weeks. She didn't go into heat again for another three months.
   
Her two sisters haven't gone into heat at all, as far as I can tell.
   
Her mother has been in heat only 3 times since July 2011, and the last two times had several months between the incidents.