Ear nibbling is one of the most interesting things one can do to their love lives. Whether in the context of sex, making out, or just saying hello, nibbling one's ear will not go unnoticed.
In addition to being a unique greeting, some people find ear nibbling very sensual. I've known people who are driven wild by the slightest bit of hot breath in the ear and a playful bite.
Really, it is quite simple, you nonchalantly move your mouth to the earlobe and gently* begin nibbling. You may or may not move up to the cartilage if you choose. For people who are better aquainted, the tongue can be used as well*.