Now that Thanksgiving's over and all the malls are putting up lights and Christmas trees, it's time to shift our fashion focus from fall colors to lumpy Christmas sweaters!

Over the past few years, ugly Christmas sweaters have become increasingly popular during the holiday season, with celebrities like Katy Perry even sporting the look on the red carpet. The extravagant colors, clumpy balls of fabric and hideous designs might make you want to cringe, but that's exactly what makes them so fun.

So what makes for the perfect ugly Christmas sweater? Think sequins, yarn and appliqué. If it seems over the top, then it's probably just right. Look for sweaters that have snowmen, reindeer, or Christmas trees on them--or a combination of all three. The sweater has lights? Even better. Your grandma knit you an embarrassing ornament sweater four years ago? Now's definitely the time to dig it out of your closet.

For those of us who don't already have an ugly sweater on hand, there are plenty of places to pick one up. Thrift stores like Goodwill and Buffalo Exchange are no longer the only places you can find these wildly entertaining pieces of clothing. Retailers like Urban Outfitters, Asos and Wildfox have now started carrying them. Of course, the ones they sell tend to be a little more fashion-forward than what you'd find at a thrift store, but they're a good compromise for anyone who doesn't want to go all out. Target, Sears, Walmart, and other bargain stores like Kohl's, K-Mart and TJ Maxx are bound to have a selection in their winter collections as well.

Once you've found your sweater for the season, how do you go about wearing it? Believe it or not, if you pair it correctly, an "ugly" Christmas sweater can actually make for an adorable outfit. Last year, for example, I bought an outrageous red sweater with gingerbread houses and reindeers embroidered on it--but once I paired it with shiny leggings and black booties, the sweater went from ugly to acceptably festive.

Here are a few tips for styling an ugly Christmas sweater:

1) With boyfriend jeans all over the place, one option is to wear a slouchy pair of those with your sweater. Throw on some slip-ons, grab a messenger bag, and you'll look cute and cozy out on the streets.

2) Take my leggings-and-booties outfit from last year and go one step further by pairing wax-coated jeans or leather leggings with your Christmas sweater. You'll be dressed for the fun occasion but still in style.

3) If you need to wear an ugly Christmas sweater to a more formal event, try it with a skirt and clutch. This might not work with every sweater.

4) Wear a simple black dress under an ugly Christmas cardigan. That way, you can show your holiday spirit, but have the option to easily take it off. 

5) Have a pleated skirt hidden somewhere in the back of your closet, but you haven't found the right time to wear it? Top it with a Christmas sweater and your favorite flats for a cuter look.

How would you wear your ugly Christmas sweater? Post in the comments below. 

Reach Fashion Columnist Beatrice Verhoeven here. Follow her on Twitter.