The Pattern to Masculine and Feminine
I recently got a book from the library that has some very useful ways to guess the gender of a noun without having seen the word before. There are some exceptions, but it is right the majority of the time.
If a noun ends in -e or -on it is feminine.
If a noun ends in -i, -u, or a consonant it is masculine.
Trees and vegetables are masculine.
Fruits are feminine.
Units of measurement are masculine (except for la livre [pound]).
Words of English origin are masculine (ex. week-end, tennis).
Languages are masculine.
Days, seasons, and months are masculine.
Source: French Grammar Drills
"If a noun ends in -e or -on it is feminine. "
L'homme and le peon disagree with you! Seriously, although there are a few rules that might help you guess, the only sure fire way is to learn the gender as you learn the word.