I usually mark the question as a "favorite" if I want to be able to have some hope of (more) easily finding it again in the future. (See the image below.)
Another alternative is, of course, to bookmark the post in your browser. I tend to do this less often as I tend to find it more, well, tedious. But I do sometimes also use browser bookmarks, just a lot less often.
Some additional suggestions
I also stumbled upon the other options in the list below while I was looking for something else. I decided to mention them here. (If nothing else this might allow me to find them again later. ;-)
- This answer on meta stackoverflow also points out that each question has its own RSS feed which you can subscribe to if you wish. I found the RSS link obfuscated at the bottom right hand corner of the page. (See also the image below.)
This option is apparently not restricted to question pages. Many other pages on the Stack Exchange sites also appear to have RSS feeds available. - This answer (to the same question) provides a reference to an App on the StackApps site which might be useful.
Note: I have not used any App from StackApps yet, so I have no idea if this is a good tool or not. - This answer appears to provide a good explanation of how to use your profile dropdown at the top of each page to sleuth out updates to your "Favorites" list.
