Here are the notes I made on gender in French when I was studying in Quebec:
1. The “Faith, Hope and Charity” Rule: Words describing a particular ideal tend to be feminine, especially if they end in “é”. Examples: “La Foi, l’Espérance, la Charité.” (But, the synonym “espoir” is masculine; see rule 2.)
2. The Rule of Specific Examples: The word for a general thing is often feminine, but a word naming a specific example of the general is usually masculine. Examples: “La terre” (the earth) becomes “le terrain” (a specific lot or plot of earth). “La règle” (“the rule”) becomes “le règlement” (a bylaw or regulation).
3. The Feminine Latinate Rule: All words ending in “-tion” without exception are feminine. These words were borrowed during the Renaissance directly from Latin. Since they are always feminine in Latin, they retained that gender in French. (Bonus! The English humanists often borrowed the same words without anglicizing them, so the same word usually, but not always, has the same meaning in English and French. If you can’t translate an English word, think of the Latinate version and use it with a French accent.)
4. The Masculine Bureau Rule: Almost every word ending in “-eau” is masculine. Examples: le bureau, le manteau. Exceptions: there are at least two exceptions to this rule: la peau (skin) and, perversely enough, l’eau itself (water; feminine).
5. The Masculine Foreigner Rule: Words borrowed from another language, especially English, tend to be masculine in French. (Subject to exceptions when the lending language uses similar gender rules as French: see rule 3). Examples: le pull-over; le week-end.
6. The Feminine Countries Rule: Names of countries ending in “e” are always feminine, with one exception. Examples: La France, la belle Angleterre, la belle Allemagne. The Exception: Le Mexique.
7. The “When in Doubt” Rule: The majority (55%) of French words are masculine. When in doubt, play the odds and assume the word’s masculine. (It makes verb conjugations and adjective accords easier, anyway.)