If you currrently use the traditional pen and paper method for taking notes, then you might like to consider the powerful benefits of using digital devices for note-taking:
Evernote allows you to create a note which can be a piece of formatted text, a full webpage or webpage excerpt, a photograph, a voice memo, or a handwritten "ink" note. Notes can also have file attachments. Notes can be sorted into folders, tagged, annotated, edited, given comments, searched, and exported as part of a notebook.
Evernote supports a number of operating system platforms (including OS X, iOS, Chrome OS, Android, Microsoft Windows, Windows Phone, BlackBerry, and webOS) and also offers online synchronisation and backup services.
Evernote is available in a paid version (very cheap) or a more restricted free version. Use of the online service is free up to a certain monthly usage limit, with additional monthly use reserved for Plus subscribers, and unlimited monthly use for Premium customers.
Microsoft OneNote gathers users’ notes (handwritten or typed), drawings, screen clippings and audio commentaries. Notes can be shared with other OneNote users over the Internet or a network. OneNote is available as a part of the Microsoft Office suite. It is also available as a free stand-alone application for Windows, Mac, Windows RT, Windows Phone, iOS, Android and Symbian. A web-based version of OneNote is provided as part of OneDrive or Office Online and enables users to edit notes via a web browser.
Finally, if you want to combine the features of note-taking via keyboard apps with the inking capability of a sketch app, you might like to try Notability (available on the iPad, iPhone and Mac).