As long as you keep running consistently, you have plenty of time.  You won't actually start a training program until about 3-4 months before the event.  For now you are building up the base mileage you need to begin training.   A good base would be when you are running 4-5 times/week for a total of about 20 miles and doing this for several months.  In the meantime, it helps to achieve some smaller goals along the way.  A half marathon is a good long term goal, but it will keep you focused if you are training for shorter races between now and then.  The racing experience you get in 5Ks and 10Ks is all part of your overall training.  Not only that, but those shorter races are a lot of fun and will give you a sense of accomplishment.

You have plenty of time to build up your base mileage.  The rule of thumb is to increase your total miles no more than about 10% weekly (if you are running 10 miles/week now, you can add a mile per week).  If you are running 3-4 miles now, go ahead and sign up for a 5K.

Good luck!

Yes you have TONS of time - Check out the Hal Higdon novice Half plan - it`s a great plan for first timers - for now keep running 3 -4 miles 3 times a  week for a few weeks  - then pick up the weekend run and slowly build that up to 6 miles - this is good base -  once you have been running this for a while you can add a 3rd run in the week no more tha 2 -3 miles - but run it faster than your normal training - or run hill repeats - up 1/4 mile hard - jog slowly down to recover .. repeat 3 or 4 times or you can do 1/4 mile sprints - run hard 1/4 mile - walk 2 mins - repeat 6 - 8 times - Pick ONE of those workouts each week - not all 3 - remember you other runs should be a slow easy pace - sloer that you plan to run your 10 K

Active just set up a half marathon training group - we will start a weekly thread so people can track progress -  etc - http://community.active.com/groups/12-marathon-trainers

Good luck, Kim!  I also used Hal Higdon's training guide for a half marathon a few years back. Unfortunately, ankle injuries denied me from entering. Ugh!  It is a GREAT template to use and don't push yourself too fast!  Keep on Chooglin'