Develop your own system of signs and symbols
Summarizing is very important while taking notes, so it will be very useful to have a system of symbols for certain things. A few standard ones like e.g., vis-à-vis and the like are there but you may also develop a few of your own. Arrows connecting a chain of thoughts written far apart may come in handy as you may not be able to make the connection later. Develop abbreviations for phrases used often. Later when you review your notes you may make them a bit more explanatory or elaborate. Do keep a record of whatever symbols and abbreviations you develop so that you have a reference point if needed. 

Using loose sheets as versus bound notebooks
Both have their own advantages and disadvantages. Bound notebooks will ensure that you have all you notes in one place. However taking notes on loose sheets has distinct advantages especially when you take notes during discussions. Assuming that you have had a discussion in class wherein many opinions were voiced, you have taken notes and have to submit a write up on the topic. Reviewing you notes and connecting different chains of thought will be easy by spreading out your sheets and being able to ‘look’ at them all at the same time.  This method comes in handy not just for discussions but even when during a lecture, questions are asked and the lecturer traces back to something he has said earlier and elaborates on the topic. When you review your notes in this case, it will be easy to connect the two discussions and form a substantial inference. 

A margin for your thoughts
Always leave a margin for that extra bit that almost always needs to be added. While reviewing your notes you will find the margins very useful to note down queries and doubts if any.

Keep your notes brief
One liners and lists are the ideal way to put down your thoughts while listening. This way not much time or attention is taken for writing, but the purpose is solved. The explanations should be present in your mind, the one liners in your notes are just the cues for prompting your memory. It is a good practice to record the date and other details of each lecture. This will come in handy especially when gaps due to absences have to be filled in.