When a mother is breastfeeding her child in a public space, these simple courtesies will help you in any situation.
1. When you happen to see a mother feeding and you make eye contact but are unsure of what to do, just smile (perhaps give a nod). CAUTION: Do not grin, she may get the impression you are a perv.
2. When you happen to get flashed (as can happen with a mobile, fussy, or curious baby), do not panic. It was an accident, not a deliberate attempt to ruin your lunch. The world survived Janet's wardrobe malfunction and your eyes will not bleed and your dinner will not spoil. After all, there is that other table with the public display of thong that you are ignoring quite nicely. Remember that your eyes are on her breasts, but her breasts aren't on your table. Turn your eyes back to your plate and resume eating.
3. When you happen to see that a mother sitting near you is struggling, sweating, and looks about to cry because the hooter hideawayer is not pleasing the baby, you can: Offer to put the titty-tent over your own head, or you can tell her not to worry about the cover and offer to stand as a shield so that she can latch the baby with a bit more freedom.
4. When you feel the compulsion to scowl because your gaze wandered to a nursing mother, remember that you were born with a neck. Turn your head before you frown. Frowning causes wrinkles.
5. When you see a mother feeding her baby in the bathroom (and you happen to be under the impression that the bathroom makes for fine dining), offer to bring your soup and sandwich into the lavatory so that you can chit-chat in side by side commodes. Otherwise, assure her that she doesn't need to nurse in an unsanitary place. Inform her that other people just don't know proper etiquette and she isn't the one being offensive. Offer to walk her out of the cloud of stench into the fresh air.
6. When you see that a woman has more breast exposed than you think is decent, ask yourself these questions: Is it more than you see on a public beach? Is it more than the bra-less double-D Harvard college nymph in the size small tank top? If the answer is no, zip your lip and turn your head. After all, are you going to walk up to those other women and tell them to cover it up? Just because the breastfeeder looks like an easy target, it doesn't mean you need to aim and fire.
7. When you see that the feed-ee is older than you think they should be to be nursing, only say something or give a disapproving snort if you're willing to write a check on the spot for the cost of formula for the next year and a half. You may also offer a cashier's check, money order, pre-paid credit card, or cash.