An indexed article in PubMed will be tagged with several MeSH terms that describe the content of the article.
When you type your search terms, PubMed will search with your words and will also search with similar MeSH terms in order to expand your search.
How can I find useful MeSH terms?
For each concept, consider using a combination of MeSH terms and words or phrases you'd expect to find in the title or abstract of a useful article.
In this example, we are looking for articles on gunshot wounds AND subsequent/recurring injuries.
In Advanced Search, enter words for each concept on a different line. Combine with AND. Search.
When you have your search results, click on "Create Alert" under the search box. Follow the prompts to save the search in your MyNCBI account and set up email alerts.
Compared to other databases, Google Scholar typically finds the most publications that cite a given article.
When you find an article in Google Scholar, click on "Cited by" underneath the reference to see publications that have cited it.
On the left side of the screen, click on "Create Alert" if you want to be notified when new publications cite this article. You will need to create a free Google account in order to do this.