SEO Audit recommend by Google Webmaster

SEO Audit Structure

The SEO should prioritize improvements with a structure like:
1. The issue
2. The suggested improvement
3. An estimate on the overall investment
4. Estimated positive business impact
5. Plan of how to iterate and improve on the implementation or how to experiment and fail fast should results not meet expectations

Technical audit

Review your site for issues related to
Internal linking
Crwalability
URL parameters
Server connectivity
Response codes

Search Audit

Break down your search queries into categories
Branded - Branded terms are those with your business or website's name like a search for Toyota  is a branded term
Unbranded - While the search for email is an unbranded or general keyword