There are a lot of different ways to get more Twitter followers. There are apps to do so, but I've never used any of them, so I can't comment on that. I like the direct, hands on approach. It takes longer, but in my estimation you end up with followers who are more interesting, and are real people, not bots. What good is having 10,000 followers, if they're mostly bots?
Method 1.) Put up a thread in the Etsy forums, under Promotions, and ask for new followers, and offer to follow them back. This results in followers who are already on Etsy, have an account set up, and know the mechanics of purchasing on Etsy. All big pluses.
Method 1.a) Search the Etsy Forum for old threads asking for Twitter followers, go down the list, and follow them -- hopefully they'll return the favor. This method involves less time on your part than the first Method, but the disadvantage is that you're not directly interacting with people on a thread. Of course, add yourself to the end of the thread, which will put it temporarily at the top of the Promotions group, which could result in a lot more people following you.
Method 2.) Do a search for #FF on Twitter. On your Twitter home page, about halfway down on the right hand column, there's a box with "search" in it. Click on the box, and enter #FF, and it'll pull up all the latest Tweets with the hashtag #FF. That stands for "Friday follows" and each Tweet will have a bunch of Tweeps listed. Click on them to follow. I like to actually go to their home page and make sure that I want to follow them. Sometimes they tweets about things I don't want to read about, or they only tweet things for sale.
Method 2.a) Like method 2.) but this time search for #etsy. Or you could search for anything you think might be helpful, like #jewelry, #knitting, #vintage, etc.
Method 3.) When you're on a blog or Facebook, look and see if they have a Twitter account, and if they do, follow away.
That's my ideas for finding new people to follow. I'd love to hear your tips on finding new people to follow, just jot them down in the comments! Next time, I'm going to blog about how to get people to follow you!