1. Make a list of URLs

Make a list of all the pages you want to rewrite titles for. (use a crawling tool if you have a large site or lots of pages)

2. Pull in Your Existing Meta Titles

Pulling your meta titles into a single list is good because;  It will show you where close duplication and crossover of targeting occurs.

3. Find Out What Your Pages Rank For

Use Search Console data to find out which keywords drive traffic to your pages.  Third party tools can help if you don't have Search Console set up.

4. Rewrite Your Titles Using Your Best Performing Keywords from Each Page at the Beginning of the Titles

Replace any close duplicated titles with unique well formed meta titles.

4. Spell Check Your Meta Titles

Run your title rewrites through a spell checker to find any issues and correct them

5. Publish Your Meta Titles & Track Performance

Upload your title tags to your pages via your CMS.  Record the date you changed them in your spreadsheet and track their performance.

Check to Make Sure CTR Increases on Your Pages Also, Look Out For Positional, Click and Impressional Improvements

Good Luck!