How to design a propeller for UAV?
It's been a long time since I did this but here's then general idea. 


Work out your requirements. 
Thrust, speed (usually cruise speed) and diameter (usually determined by the available space) being the key ones.
Use a piece of software such as this one to optimise other design parameters for your requirements.
You may also consider off-design (non-cruise) performance. 


The link above also contains more details about the design process and considerations.