The the feminine nouns often end in ة or with an attached personal ending there is a ت between the pronoun and the rest of the word because the ة gets split open when you attach a letter to it. BUT there are exceptions. At this level they keep it simple, so look for ة. I'll give you one exception, the name حمزة (Hamza) ends with ة but it is a masculine name.
Sometimes all you can do is memorize. In Arabic, body parts that come in pairs are grammatically feminine and many nature words like sun, sky, earth, and fire (etc, however there are still exceptions, it is not a rule -> moon is masculine) are feminine.