Cats usually go into heat for the first time around 6 months old. If it is an indoor cat she will drive you crazy trying to get outside. There meow will change.  she will get these really deep strange meows. If you go to pet her around her tail area she will "prime"  herself. You know, get in the position.(backing up, low to the ground, tail to the side.

 A cat's cycle is variable--they can cycle on 10-20 day intervals.  This can lead to up to 3 litters per year.  They do go into a seasonal anestrus--where they do not cycle in the winter and fall. 
Cats in heat may have behavioral changes, vocalize, and become affectionate.
I would have your cat examined by a veterinarian to make sure there is not an underlying urinary tract infection leading to inappropriate urination.  If this behavior is due to hormones then spaying will be the fix.