For this challenge, a series is defined as a collection of two or more books that belong together and where the second book is published before the end of 2014. This is a pretty broad definition of series, and it includes traditional series like the Black Dagger Brotherhood series, less traditional series like Stephanie Perkins's YA contemps (Anna and the French Kiss, Lola and the Boy Next Door), and shorter series, like Kendare Blake's Anna series (Anna Dressed in Blood, Girl of Nightmares).
A series is considered complete in one of two ways: either as finishing all the books that you own in the series or as obtaining and reading all the books that have been published in the series to date. Because we don't want this challenge to become a financial burden, how you choose to define completion is left to your discretion.
How It Works
To allow for the greatest level of flexibility, we've separated series into three categories: series started before 2014, series started in 2014, and series rereads.
Series started before 2014 are defined as series that you have started reading before Jan. 2014 and that you still have unread books to get current in (or finish) the series.
Series started in 2014 are defined as any series that you start reading between Jan. and Dec. 2014, and the second book in the series must be published before December 2014.
A series reread is defined as books that are part of a series that were read before Jan. 2014 and that are reread between Jan. 2014 and Dec. 2014. A series reread does NOT have to include the full series.
For each category, there are different levels of seriousness about series that you can choose. Semi-serious is reading 1 to 6 series, seriously serious is reading 7 to 12 series, super seriously serious is reading 13 to 18 series, and seriously spectacular series star is reading more than 18 series. What this ends up looking like is this:

series started before 2014series started in 2014series rereads

Semi-Serious1-6 series1-61-6

Seriously Serious7-127-127-12

Super Seriously Serious13-1813-1813-18

Seriously Spectacular Series Star18+18+18+
FYI, reading novellas and short stories from a series does count here -- if you want it to!

You choose which categories you want to attempt and which level to shoot for.
Goals and Progress
Want to sign up? Create a post or page about this challenge, what goals you would like to accomplish (mine is here, as an example--currently, it's my 2013 page, but it'll switch over to the 2014 challenge in January), and then link up your post here at Reading the Paranormal. In addition to the sign up, every three months, there will be a check-in, where you can report your progress and reassess your original goals. That schedule will look like the following:
April 1st: January--March
July 1st: April--June
October 1st: July--September
January 1st, 2015: October--December

I have a ton of partial series laying around the house. This challenge is to get me to clean out some of those series. I have lots of authors on my list to choose from, but I am only committing myself to finishing 5 old series and 5 new series throughout this coming year. So I am going for the semi-serious level for two categories.

Started before 2014:

Locke and Key -- #6
Opal Cowan by Maria Snyder -- #2, #3
Bevelstoke by Julia Quinn -- #2, #3
Living with the Dead by Jesse Petersen -- #3.5, #4
Ashfall by Mike Mullin -- #3

Started in 2014: Going with just author names right now. Some of these authors have multiple series that I can start...

Diana Gabaldon
Mary Balogh
Holly Black
Gregory Maguire
Cherie Priest
Anne Bishop
Kristen Callihan
Carole Nelson Douglas
Dorothy Dunnett
Jeaniene Frost
Diane Haeger
Karen Marie Moning
Deanna Raybourn
Melissa Mayhue
Julia Quinn