If your New Year's Resolution is to kick your Etsy sales up a notch, you've come to the right place! I've been actively running my Etsy shop for just over one year now, and I've definitely learned a lot in the past year. If I had to give only one piece of advice to a new Etsy seller, it would be this: Consistency is Key.
I'll admit it: I haven't been a particularly consistent Etsy seller. I tend to get all excited about something, like selling on Etsy, put a lot of time into it for a few days or weeks, and then promptly forget all about it. While there's something to be said for the idea that having something listed on Etsy is better than nothing, you'll fare a lot better as a seller if you are consistently listing new items and renewing old ones.
If possible, it's definitely best to add new items often and consistently. I don't always do this, but I make the most sales when I do. Instead of posting 20 items all in one day and then nothing for a few months, you'll have much better luck if you post one item every day for 20 days. This ensures that your listing stays close to the top of searches. Once you get buried, it's really hard for your potential customers to find you. If you don't have that many items to sell, but you sell multiples of that item (like custom necklaces or something), relist that same item a few times, but maybe vary the first picture with the listings. I currently have my custom dictionary brooches listed about three times.
How to maintain consistency? Set a schedule for yourself and stick to it. This is something that I didn't do in the beginning, which is why I had sluggish sales. Sure, I sold a few things a month, sometimes a few things a week, but I could have been doing a lot better all long if I'd be more consistent about my time spent on Etsy. Think of it this way: the more time you put it, the more you'll get out. Try and devote at the very least one hour a week to working on your Etsy shop. Very likely, you'll find yourself spending more time, but stick to that one hour a week thing on the weeks when you are insanely busy. Tell yourself it's only an hour and just do it already!
What to do in that one hour? Add new items, renew current items, and research tags. Find people who are selling items similar to yours and see what they are using to tag their items. Check out Shades of Color on Wikipedia and make sure you are tagging your items with the best color words you can. Improve your photography skills. Build a lightbox if you don't already have one and practice, practice, practice. You don't even need a fancy digital camera: mine is a Fujifilm A205 which sells for about $40 on eBay. I love it! Improving your photography skills is probably the number one thing you can do to improve your chances of success of Etsy, so add it to your to-do list.
Make a commitment today to spending at least one hour every single week this year working on your Etsy shop. Stick to you and come back 52 weeks from now and tell me how your year went! I'm willing to bet that if you commit to actively improving your shop, you'll see improved sales numbers to match that effort!
That being said, there's definitely merit in sometimes posting a whole crapload of items all at once. Over the most recent Black Friday weekend, I decided to take the opportunity to really beef up my store. I had tons of items in my inventory from my summer sales and have been meaning to post 'em online for months. I posted over 100 items on Black Friday alone, which was, well, crazy! But you know what? I made 12 sales, the most I've ever made in one day (or, hell, one week!), so the overload strategy must have worked. In the week following Black Friday, I made over $500 in sales, which was probably more than I made in the whole year prior to that one crazy overload Etsy day.
I read in the etsy forums a post by a successful seller who said that if you aren't paying a lot in fees, you aren't listing enough on etsy. That totally makes sense to me! My etsy bill is currently $75 or so, but I easily covered that from my Black Friday sales & all those items are still good for 4 months, if they don't sell sooner. Totally worth it.