Math syntax
Obsidian uses MathJax. I include some common commands on my MathJax page, but here I will put Obsidian related considerations.
New line management
It seems newlines are not supported in Obsidian, which, within a math block seems to normally be \\. But, this has no effect within Obsidian, as far as I can tell.
One workaround is using successive inline equations (single $). The equations are tightly packed, but left-aligned.
Another workaround is using successive block equations (double $$). The equations are centered but more spaced out.
When not to embed content
TLDR: cmd-hover a block reference to view it quickly without having to embed it.
Embedding content can take up a lot of space in a note. Consider referencing it instead and viewing the content via the cmd-hover popup, or cmd-opt-click split tab.
Search for any block in your vault
You can type [[^^]] to reference/embed any block in any document in your vault.
You do not get advanced search terms. It is the basic match-any search, which can be hard to narrow. For this reason, it is often easier/faster to use the normal link to blocks flow.
An example of when I find this useful is referencing a unique quote from a book without remembering which book it was from. If I don't find it quickly, I use the search functionality instead.
Embed a webpage with full width and fixed height
Use an iframe with width set to "100%"
<iframe
src="https://en.m.wikipedia.org/wiki/Jane_Eyre"
width="100%"
height="500"
></iframe>
Use mobile version of web pages
For example, the mobile version of english wikipedia is en.m.wiki... instead of en.wiki.... It creates a more readable experience. Additionally, navigating mobile pages will keep it in mobile.
Don't use reference style links
Introduction to reference-style links (independent of Obsidian).
Reference style links are not supported, and lead to odd behaviors. There is a bug report in the forum, so it is at least known. (It's non-trivial to support for a variety of reasons.)
My current solution is to copy and paste the link every time I reuse it. It has already led to mistaken links I don't catch, etc., so hopefully I can find a better solution soon.
It is valid markdown, so if you read/process the file external to Obsidian, it will still work, but internal to Obsidian it will create a non-sense file in your vault if you click on it.
Edit headers by right clicking on them
If you edit a header manually, it will not update anywhere you have referenced that header. This results in dead links.
The solution is to right click the header when you want to edit it. In the dropdown, choose "Rename". Doing it that way will update it everywhere it is referenced.
That same dropdown will allow you to do other powerful things, like extract headers in to new notes, or extract selected text in to new notes.