1. Too much highlight on your brow bone
Instead of actually enhancing it, too much highlight on your brow bone will only make you look oily and shiny.
2. Unnatural brows
Whether they are too high, too thin or just a weird shape, don't wander down the path of unnatural brows. You can check out this post for help with brow grooming.
3. Miss matched foundation/concealor
Whether you are trying to make your dark circles look lighter or your face look tanner, don't try to fix your skin tone with mismatched foundation. You won't fool anyone!
If you put on tons of mascara, people aren't going to think "wow her lashes are so long!" Instead they are going to think "wow she has on tons of mascara!" If you really want longer lashes, try Lilash or getting lash extensions instead.
5. Makeup overload
A really heavy eye, with a full-on lip, with a face of full of foundation, plus bronzer and blush is only going to make you look like a drag queen. Unless you are a drag queen, pick just one feature to enhance instead of your whole face.
6. Unblended eyeshadow
The purpose of eyeshadow is to add depth to your eyes, and to enhance them. If your eyeshadow isn't blended, it won't do either of those things, and you will look like a clown.