Meta description, 70–165 characters The grey line Google prints under your title. Without one, Google picks a sentence off your page at random.
Mobile viewport declared Without this line phones render your site zoomed out and unreadable. Most of your customers are on a phone.
One clear H1 heading One main heading tells search engines what the page is about. None or several is ambiguous.
Structured data (JSON-LD or microdata) Machine-readable facts - address, phone, hours. This is what puts a business in a map card instead of a plain link.
llms.txt or AGENTS.md for AI search Plain text files that tell ChatGPT and Perplexity what your business does. Almost nobody in Austin has one yet.