This is a very terse collection of notes to myself about things I find useful to remember or think about when constructing a new language. It's less about rules and more about reminders of possibilities. Probably some of it will not be very useful to anyone who doesn't think very much like I do, but good chunks should be generally useful.
The section on sound changes is largely from the Index Diachronica, but some items from other sources have made their way into it over time.
If you don't want to LaTeX it yourself: Hypomnemata Glossopoetica.
You will need The Brill typeface (or change it to some other Unicode, IPA and small caps capable font in the LaTeX source, such as Libertinus).
You will need XeTeX (part of LaTeX).
xelatex hypomnemata