I know it can feel rather frustrating to learn the gender rules to soon find out that there are a few common exceptions. So what can you do to tell a noun's gender? Toss a coin? 
I’ve got a better idea. I want to share with you a tip that works wonders. Just follow the following three steps:
 

#1 Pick a word like ‘la mano’. 
 

#2 Associate the word mano to a girl/woman you know.
 

#3 Write down a Spanish sentence with ‘mano’. 

Let me give you an example. Let’s say you have a daughter called Mia. Then you could write:
 

La mano de Mia es pequeña.
Mia’s hand is small.
 

Every time you think of the word ‘mano’, you’ll be thinking of Mia, and voilà, you’ll know it’s feminine.
It’s cool, isn’t it?