How can you distinguish between twins?

I do not have twins, but to come and think of it, it must be quite amusing to mix up when feeding the babies. I think to be sure who is who, mums can dress them in different clothes, so by keeping the clothes in mind the mum is not confused. And if you want to dress the babies in same clothes, as they would look cuter that way, then you can embroider the names of the babies at the back of the dress or mark their names with waterproof maker. Or, you can also look for some birth mark or may be if the complexion is one shade light or dark, you can make out who is who. Or you can put a nail print on the toe of one baby and leave the other one's. This way also you can make out the difference.