Applying darkest eyeshadow to your crease or lids first. Apply a lighter one for a better blending. Dark eyeshadow should be used minimally to add accent. It is easier to add some dark color than to remove it from your lids.
Forgetting to dust the pigment off the brush.
Using the same brush for blending and adding color. Use a smaller brush for lower lash line.
Not using a clean brush for blending a new color.
Applying shimmery shades with a dry brush. Wet it slightly in setting spray or use glitter primer.
Not having a reference point for your wing liner. It should always point where your eyebrow ends.
Keeping eyeliner thick in the inner corner. It should be thin in the inner corner.
Clumpy mascara.
Too much highlight. Apply it just under the arch of your brow, do not drag it further and put just a neat dot on the inner corner.