Craft weasel has come out with this new fantastic tool to help you with your tagging! I tried it and it showed me not only a whole bunch of tags that might go with my item but it shows you a graph of price, a graph of views per day, a graph of the tags that are most viewed and so on. I think I will be using this tool quite often to try and get the most productive tags possible!!! Check it out!
Also try out the Stat Finder. You can get your own stats on which tags are working for you. All you have to do is type in your Etsy shop name. It's so easy! Check it out!