Setting up DNS so local/internat hosts resolve between each other?

Is there a recent guide for getting DNS set up locally? I seem to have a lot of issues with devices on my network resolving each other's hosts and it's driving me nuts

Sometimes adding a . on the end of the host works, sometimes .local works, and sometimes nothing works.

Windows and iOS devices really struggle. All external name resolution works fine.

Anyway, is there a guide to do this? I have a "real" domain I can use for this stuff if it would help.

Thanks