Go to this link there is scientific video about how to use the hemacytometer, my help you. it only needs to create account to be able to listen to the videos.

http://www.jove.com/science-education-database/2/basic-methods-in-cellular-and-molecular-biology

This could help you:

http://bitesizebio.com/13687/cell-counting-with-a-hemocytometer-easy-as-1-2-3/

an online calculator:

http://www.hemocytometer.org/hemocytometer-calculator/

yes - sterilize your tween solution

Thank you guys. Big help for my thesis. God Bless