Problem: Low Open Rates - The fault will lie fairly and squarely with your subject line, it is not working hard enough to stand out from the crowd.
Answer: Simply spruce up your subject. I include a link to an earlier mail that goes into what you can do to create good headlines in some detail:
Problem: Low Clickthrough Rates - The content of the mail and/or the call to action are at fault. You have not connected with the reader enough for them to take an action.
Answer: work on writing your mails as you would to a friend. Make them engaging with stories, analogies and personal experiences. 'Sell' the benefits of the offer you are promoting. Also make sure your 'call to action' ie the comments to get the reader to click on your links, are obvious and leave no ambiguity e.g 'To find out more click below now', 'Click HERE now to find out more' etc.
Problem: High Unsubscribe Rates - Every time you send a mail you get a whole bunch of 'Unsubscribes'. This can be for a variety of regions, but at the core is that the reader does not relate enough to you and your mails. This is not necessarily a problem if you want to attract and keep just those people who are going to be responsive to your mails. You will ALWAYS have unsubscribers every time you send a mail, only worry if this number is increasing.
Answer: See the answer above to making the mail worth reading. Also make sure the mails are relevant to the reader. If you attracted subscribers by giving away a guide on dog training, make sure your mails have at least some link (even if indirectly) with dog training. (And remember if you send out mails, you WILL get unsubscribes, see this as a positive thing ensuring only the most responsive individuals stay on your list.)
I hope this helps and please feel free to add any techniques you personally use to overcome the issues I mention here.
All the best