Put
![](before)
after.
First head is lacking flow and concept. It seems like you planned out the front, then just did the rest to fill in the empty space.
Second head is quite good, but try using a softer brush to shade and raising the eyes up a little.
Third head appears to be brush spam.
Overall, you could use a lot of improvement.Try starting with an idea in your head, and going through with that idea to the best of your ability.