Should I put keywords in my title tag or write it for people?

Do both in the same line. The title tag has 2 jobs: tell search engines what the page is about, and persuade a person to click.

A workable formula:

• Start with the words a searcher would type, in the order they would say them.
• Add the specific thing that separates this page: a location, a price range, a number, a format.
• End with your brand name if there is room.

Compare "Plumbing Services | Home" with "Emergency plumber in Meriden, CT: 24-hour repair". The second one matches how people search and promises something concrete.

Rules that hold up:

1. Make each title unique. Two pages with the same title compete and confuse everyone.
2. Keep it readable at the length it shows. There is no hard character limit. Google cuts titles by pixel width, which is roughly 50 to 60 characters on desktop. Put the important words first so a cut does not hurt.
3. Match the page. Google may rewrite a title it thinks does not describe the page, often when it is stuffed or generic.
4. Do not repeat the keyword. One natural mention beats three. Stuffing reads badly and gains nothing.
5. Test with data. After a change, watch click-through rate for the page's main queries in Search Console over a few weeks. Compare against queries whose titles you did not change.

Remember that the H1 and the title do not have to be identical. The title is written for the results page. The H1 is written for someone who has already arrived.