Here is what you need to know:
1. Concealer should match your skin tone or be one shade lighter. Please avoid using colors like green or orange if you do not know how...unless it is Halloween.
2. Use it to cover dark circles around the eyes, and any discoloration on the face, pimple etc.... not to draw crop circles on your face...
3. Concealer is not a highlighter.
4. Use it only where needed, and little goes a long way....
5. For extreme cases apply concealer over foundation so it will cover and not be rubbed off, but make sure you blend it in completely.
Please keep in mind there are no set rules to makeup or makeup application, just suggestions or tips....go wild :)