I have a strategy of only writing key words or phrases and noting things that are emphasized. For example, my notes on the previous sentence would simply be "notes-key words".
I split understanding and summarizing personally, because understanding is more about being able to replicate the methods used, while summarizing is about condensing the lesson into a key point that could aid understanding. I personally find that the summarizing technique does not aid understanding any more than simply following along with the logic and concentrating fully on why it's happening.
Obviously some people may require that extra summarized step to allow them to recall the lesson, but I've been able to do without it by concentrating on the flow and linking it to other knowledge that I've already internalized. That way you don't need those key points jotted down for later - you just need to reason about where you're trying to go and use the understanding to plot a course. Then look up the steps where you know you're unclear on the details in a textbook or web search.
I do make use of mind-mapping now, though. It's handy for dissecting a big linear text into branches and partitions and not overlooking parts when I try to review.