One of my most favorite traditional things to do is getting henna done. It is put on to celebrate different life events: weddings, births, big holidays. There are typically three different styles of henna. The first is very old school where the fingers are solid with a rounded shape and pointed shape on the palm. (I'm sure there's some symbolism but I've asked around and haven't gotten a definitive answer.) The second is a design that varies by the artist. You can either use a stencil that sticks to your skin and the henna paste is rubbed into it or the artist will use a piping bag to freehand a design. The third is a simple circle in the center of the palm.
Once the henna is applied the idea is to get it hot so the henna will stain your skin either a black or mahogany brown. This means wrapping your hands and feet in cotton and then stuffing them in plastic bags (and in some cases sitting in front of a heater on a hot summer's day). The more patient you are the darker the color will set and the longer it will last.
Depending on how long you let it sit, how many dishes you wash afterwards, and the general nature of your skin, the henna will stay between two and four weeks. For the first few days there's a very distinct smells that comes along with the color. It's one of those you either love it or you hate it very earthy smells. (Fortunately I'm in the "I love it" category.)
Henna is a fun way of letting the whole world know "HEY! Something good happened in my life!"