This won't be news to everyone but a super easy win is good segmentation. I'm amazed to see how many batch and blast emails still exist, or emails sent to me about summer when it's my winter. It can be as simple as making sure the seasons are right! You may not know everything about your users but we are already finding out something as broad as segmenting out regular users vs information workers increased our unique click rates. I think this is because information workers are used to clicking on emails. Good information to know.
