Agreement of gender
Native speakers of English rarely have trouble with gender. Foreign speakers should realise that we natives find it very strange to hear sentences like "My wife,
he is asleep" or "My son, she is at school".
One area that sometimes gives problems to all of us is usage that seems to treat men as superior to women. (The other way around, treating women as superior to men, is much less usual in our society - or indeed less simple in our language.) Some feminists reject the use of Chairman, for example, instead of Chair to mean the presiding person at a meeting whatever the gender of the person. Some women, on the other hand - notably the current (2012) co-Chairman of the Conservative Party, a woman (Baroness Warsi) - insist that Chairman is a traditional term to be used for men and women alike.
AWE's advice to writers on this is, as in other areas, consider your audience. Who is likely to read this? Will your readers be offended by certain usages? Do you want to offend them? In general, a writer should try to avoid offending an audience unless deliberately - by choice.