How to write neatly with pen and paper?
My daughter has Cerebral Palsy and writes quite well thanks to a few tricks she learned from an Occupational Therapist.


Get a fat pencil or you can get a plastic sleeve that goes over a pencil.
Use a soft pencil lead available in many stores, especially art stores.  I recommend HB, or 2B.  It is easier to control a soft pencil.
Rest your forearm on a table when writing, not just the palm of your hand for better control.  


This works for anyone, not just folks with physical issues.  Now that I am getting older, this works for me, too. Once your brain gets the message, these tricks become less important.