Resources for Search Engine Optimisation
Each article listed below takes one task from start to finish, so pick the one that matches the problem in front of you. If you are new to the subject, begin with the SEO glossary, which explains more than 80 of the terms you will meet in reports and agency proposals in plain English. If you already suspect something is wrong with the site, the SEO checker guide and the website analysis guide help you pin it down and decide which faults to fix first.
Whichever guide you start with, record the clicks and impressions for the page you are working on in Search Console ahead of any change. Make one change at a time and compare the same length of period about a month later. That way you know which change made the difference, and a good change is not hidden by a weaker one made alongside it.