In the sidebar write keywords or main ideas from the paragraphs. Condense to the most important. Use mnemonic techniques, such as acronyms made from important groups of words. Put ideas in your own words. Use the sidebar when reviewing for tests and then check your more complete notes for the ideas which need more review.
Some people find concept mapping useful when reviewing or condensing notes.
Start with clean unlined paper. Print in capitals to keep points brief. Put the main idea or concept in the middle of the sheet. Around it make branches for groups of related words and ideas. You can use lines, arrows, branches to link lists, groups or flows of ideas.