People take notes in Obsidian in a lot of ways for a lot of reasons. But perhaps you want to just get started, so here is a simple recipe for better notes using Obsidian.
Stage 1: Write anything
Write anything in Obsidian. Common things you might like to write are things you are thinking about, your plans, or a log of something you are doing, or notes about what you find when you are searching for them.
Stage 2: Tag your page and link it to something
Think of a tag for what your are writing about. If your page is related to something else link to that page.
Stage 3: Search for content some time
At some stage you might want to find something you have already created either for reference or to add to it. Use Obsidian Search to do this. If it is hard to find maybe add some different tags, some links, or some keywords.
Stage 4: After search, extract content or add something else
When you look for your note and use it is a good to clean it up and extract information out so it is a big more usable. If you feel like your notes could be easier to read, or a little more general, or there is something else to say, create new note - extract out the content that is relevant and then link back to your original content.
Stage 5: Repeat a lot
If you repeat this over a while eventually your notes with start to get more structure.
Stage 6: Maybe do some learning or thinking about notes
If you do this and find that Obsidian is actually useful to you. You might be interested in reading about note taking in Obsidian to get a few “tricks” to apply, or starting to automate Obsidian and make it more usable or do the precise thing that you want.