Use whatever you are comfortable with. I'd suggest starting with something basic for recording notes like Notepad++. The important thing is to be able to keep detailed notes about your session, to setup a session charter, etc. Once you've got some practice with it, you can see what works and what doesn't.
I've used Rapid Reporter and Session Tester as ...
Not saying that it's cheap, but, tools like OneNote tend to fill this void very well. We use a notebook for each application. For projects, we use Tabs/Sections for Modules/areas, and for operational type changes, we use a new section for each Release. Each session takes up 1 page. These get stored on either a sharepoint or in a shared folder that we all ...
A charter sets out what you should be exploring during a test session.
For example, a charter could be 'Explore the Settings feature of the website for a logged in user'.
A test session would then be used to fulfill this charter. Test sessions are usually time-boxed to some extent - for example, 90 minutes.
One more documentation tool for session-based test management for your consideration: qTrace
qTrace includes the option to capture and display timestamp associated with every screen and action along with user's action. Besides, the duration of the record is also captured. Also, the timestamp feature is available in free edition.