1. Everybody does it differently. If you think you might have a negative reaction to one of the components in the scent (for me, anything with lavendar, or clove, etc) or you just have sensitive skin, try only a little dot of oil in an easily-washable place, like the inside of your wrist, so you can smell it to see what it's like, but if you hate it or you react to it, you can wash it off quickly.

2. If I'm trying the scent, I use the wand. I overkill things, so I just wick the wand over my skin -- you can dot it, anything you want. In anything but a very, very empty imp, the wand will come out with some oil on it, so just use that without redipping.

3. However long you think necessary. Some oils dry down very fast, which means the change in scent is pronounced. Sometime it takes a while. Here's an example of what I'm wearing now, Jack, which is my OMG FAVORITE fall scent, although I want the Pumpkin Patch 2007 series muchly.

In the bottle: pumpkin, pumpkin, pumpkin.

Wet on skin: more pumpkin with a little clove

An hour later: the scent starts getting more peach and lightens up.

Two to three hours after that: pure yumminess.

But there's no hard or fast rule, it's just when you start noticing the changes in the scent.