I'm always hot. And sweat frequently from the simplest of things. How can I stop sweating?

Prone to sweat! You probably can't if you have always been this way. However if you have disabling sweating from your palms interfering with your activity certain procedures can be done to denervate the sweat glands. Google hyperhidrosis perhaps the mayo clinic web site may also provide useful information.
Check your thyroid. Tjis can be related to an over functioning thyroid.