Forget whether or not to put your keyword in it, make it relevant to a searcher and write it for humans, not search engines. If you want to have this 20-word meta description which accurately describes the page you have optimised (for one or two keyword phrases) when people use Google to search, make sure the keyword is in there. There is more likelihood it will be used by Google as your snippet description in SERPs.
Search engines may penalize sites they discover using black or grey hat methods, either by reducing their rankings or eliminating their listings from their databases altogether. Such penalties can be applied either automatically by the search engines' algorithms, or by a manual site review. One example was the February 2006 Google removal of both BMW Germany and Ricoh Germany for use of deceptive practices.[54] Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google's search engine results page.[55]

A breadcrumb is a row of internal links at the top or bottom of the page that allows visitors to quickly navigate back to a previous section or the root page. Many breadcrumbs have the most general page (usually the root page) as the first, leftmost link and list the more specific sections out to the right. We recommend using breadcrumb structured data markup28 when showing breadcrumbs.

Write a description that would both inform and interest users if they saw your description meta tag as a snippet in a search result. While there's no minimal or maximal length for the text in a description meta tag, we recommend making sure that it's long enough to be fully shown in Search (note that users may see different sized snippets depending on how and where they search), and contains all the relevant information users would need to determine whether the page will be useful and relevant to them.

Linking to a page with actual key-phrases in the link help a great deal in all search engines when you want to feature for specific key terms. For example; “SEO Scotland” as opposed to or “click here“. Saying that – in 2019, Google is punishing manipulative anchor text very aggressively, so be sensible – and stick to brand mentions and plain URL links that build authority with less risk. I rarely ever optimise for grammatically incorrect terms these days (especially with links).

Another excellent guide is Google’s “Search Engine Optimization Starter Guide.” This is a free PDF download that covers basic tips that Google provides to its own employees on how to get listed. You’ll find it here. Also well worth checking out is Moz’s “Beginner’s Guide To SEO,” which you’ll find here, and the SEO Success Pyramid from Small Business Search Marketing.