Follow ICH Q2(r1).  This guidance can be useful even a non pharmaceutical or biopharmaceutical.  Review the many articles in online journals on how people do it.

Write your protocol stating how you are going to validate the method. Before it is signed try it out.  This is called pre-validation.

Validate the method.  Get results and have them reviewed by a competent person.

Finally, write your final report on the validation results and have the same people who signed the protocol sign this report.

For method development read Snyder's book on Modern HPLC and follow John Dolan.  Review websites;

http://www.chromforum.org

www.chromacademy.com

https://www.sepscience.com

Who knew?

http://www.chromacademy.com/chromatography-Art-of-HPLC-Method-Development.html

With ICH Q2(r1) you may also refer USP for getting knowledge about method validation (Validation of compandial methods). Hope this will help you.

Start with this tutorial,  then follow the above-mentioned resources. 

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.rsc.org/images/Warwick2_tcm18-93083.pdf&ved=0ahUKEwihv6Xbv9rTAhXEHxoKHV2RBkUQFggmMAQ&usg=AFQjCNHjltHsb4uA90FTSMZAXkgKbeg4mw&sig2=Gn_zJaBNY0RhvoE5KhSXxw 

Follow ICH GUIDELINE VALIDATION OF ANALYTICAL PROCEDURES: TEXT AND METHODOLOGY Q2(R1).

Also you can follow this reference:

HPLC for Pharmaceutical Scientists

edited by:

Yuri Kazakevich & Rosario Lobrutto