Taking Notes
Use notekeeping tools to write key information down for later referral. Write down the actual commands and take screenshots!
Information from different sources can be brought together in one notebook, but several notebooks on different topics are also sensible to keep the complexity under control.
Notekeeping tools can also be used to put information together while conducting the pentest. Make sure to store IP address and date. Checkmarks can be added when the finding has been included in the final report.
Use an image editor, e.g. to add a border, invert colors (especially when working in dark mode!), obfuscate information, copy to clipboard and from there into notekeeping tool.
For notekeeping: Windows: KeepNote (not updated for a while!), OneNote, Linux: Cherrytree For screenshots: Windows: Greenshot, Linux: Flameshot
Pen and paper is also a possible alternative!