SEO is a slow, technical and partly unpredictable discipline, which makes it easy to oversell. These are the warning signs worth checking in any SEO proposal, with the questions that test each one.
A guaranteed ranking
Search engines decide rankings and no agency controls them. A guarantee usually means the agency has chosen easy terms, or plans to count something other than real rankings. Ask which keywords, on which search engine, from which location, and how a ranking is verified.
Work that is only reports
A good proposal lists what will change on your site and in your content each month. If the deliverable is mainly a report, ask what actions the report will lead to, and who will carry them out.
Bulk or bought links
Links from relevant, trusted sites help. Large packages of cheap links from directories or link networks can lead to penalties. Ask how links are earned, and ask for examples you can open and check.
Content written for search engines
Pages stuffed with keywords or generated in bulk rarely help and can harm a site. Ask who writes the content, what they know about your field and how it will be reviewed for accuracy.
No access or no ownership
You should have access to your analytics, your search console and your site. Be careful of agencies that keep these accounts or build the site on a platform you cannot move.
Vague timelines
Most sites need months before the effect of SEO is clear. A proposal that promises results in weeks should explain what will change in that time and how it is measured.
Use a free check as a starting point
MarketRank's free SEO checker reads one page and reports on its title, description, headings, indexing rules and sitemap. It does not rank your site, but it shows whether the basics are in place before you pay for an audit.