I wanted to share some tips for all you clan leaders out there on how to effectively lead your clan. These aren't in any particular order.
1) Lead by example
If you want your clan to participate, you need to participate. Play in as many challenges and earn as much XP as you can to help out.
2) Team up with your clan members
Try to play with as many clan members as you can. Try not to just stick with the same ones every time. It will help them feel like they are a part of the team. It is easy to get used to just playing with the same people all the time, but try to mix it up from time to time.
3) Define what your clan is about
Are you campers, quick scopers, run and gunners, college buddies, people in the same state, etc. Determine what the requirements are for people to join your clan. You need to know this early on. Just accepting anyone into the clan may not be the best way to go. It's easy to get desperate for more players, but don't just take anyone. Take the people who will play the way you are wanting them to. For some it may not be about how good they are but instead that they live in their state (for better connections). For others, it may be that they have similar beliefs, or that they have to have a certain K/D ratio.
4) Manage the clan in a timely manner
Enlist the clan in operations, respond to invites, respond to messages from your clan members. If you run a website, keep it up to date in a timely fashion.
5) Treat your members with respect
Realize that your members have lives outside of the game. Expecting them to be online for every challenge and every day is not very realistic for most clans. If you sit there and criticize your members for a bad game or for something they did, you will end up with your clan members not respecting you. if you show respect you will likely get it returned to you.
6) Communicate with your clan members
Communication is key to succeeding with your clan. Communicating on the platform may not be the easiest way. A Facebook page, twitter, website, or email list will often be some of the best options. Utilize the COD Application to help with this as well.
7) Create a website
This isn't necessary, but it is helpful to bring everyone together. You can create your own from scratch which requires a lot more work or you can use a clan hosting service like COD Clan Pages (http://www.codcp.com) which is built around this game already and builds upon the shortcomings of the official application/website. The website can help with communication as well so people can easily see what is going on. Just be sure to keep it up to date and accurate, otherwise it becomes useless to your clan mates. You can see a sample website at http://lfjc.codcp.com. Another popular service is Enjin but I don't know much about it...I'd suggest Googling it.
8) Maintain the clan
Over time, people may stop playing the game. Feel free to remove them from the clan or move them into an "inactive" rank so people know who the active members are. This is helpful when looking for people to team up with. If you have a clan structure, keep it up to date.
9) Pay Attention
Watch the news related to the game (title updates, changes to how things have worked in the past, etc). Be aware of what is going on in the game and any special events such as Double XP events and make sure to let your teammates know about this. Know what game modes are available. Know the rules around the clan and how all the clan functionality works. You should be a source of information for your members. If you don't know what's going on with the game, then you aren't helping your clan members either.
10) Engage your members
Keep your members engaged in the game. Make sure they are aware of events that are going on, title updates that have occurred, ways they can help out with the clan. Do a contest with your clan members where only they are eligible to win a map pack. Collect feedback from them about how you are doing and how the clan is doing by doing a survey.
These are obviously my opinion and I don't necessarily follow each of these to a T but I wanted to put them out there either way. Feel free to discuss anything I may be missing or that you may disagree with.