Build a real list rather than a database
Ten journalists you have actually read beats a thousand contacts bought from a media database. Find them by searching your category on Google News and noting who keeps appearing.
Read their recent work before you write. If your pitch could have gone to any of them unchanged, it will get deleted by all of them.
Give them something to file
The strongest angles are original data from your own business, a genuine first, an expert view on something happening this week, or a counterintuitive finding. A funding round or a new hire is not a story outside trade press.
Put the story in the subject line and the first sentence. Journalists decide in seconds.
Follow up once, then move on
One follow-up after three days is fine. Two is pushing it. Three makes you the person they mute. Keep the list and come back with a better story next month.