What to put in a monthly newsletter
If you're staring at a blank page every month, the format is the problem.
Three blocks, every month
A tip, a recent job (with a photo), a heads-up about the season ahead. Same three blocks, every issue. Removes the 'what do I write' question entirely.
Short paragraphs, plain words
Three to four short paragraphs. Read in a minute. Marketing-speak gets ignored. Owner-voice doesn't.
One call to action, soft
A single line at the end ('Reply if you want me to take a look at your [thing]') outperforms aggressive sales asks for newsletters.
Take your version of this question further
This is one operator-tested angle on the question. Your shop, your size, your trade, and your team change the answer. Ask your specific version inside Ask a Shop Owner to get a response grounded in how owners like you actually handled it.