For me it comes down to writing down a quick impression of what it is I'm learning. For this I use Notepad++. Then I go back the same day and rewrite my notes w

For me it comes down to writing down a quick impression of what it is I'm learning. For this I use Notepad++. Then I go back the same day and rewrite my notes while the topic is fresh in mind. The rewritten notes go into Zim Wiki for long term storage. This method has worked well for me for several years now. The tools don't matter though, but the method does. Modify it as needed to suit your own style and needs :)