OK some advice
1-Start small. Trust me you're going to go through several milestones, enjoy them all. First time running for 1 mile non stop is always a good one. First 5K, first 10K. Pick races/events that you think look cool is for a cause you support, there is something almost every weekend.
2-Do it for the right reasons. I cant emphasize this enough, don't take up running or any activity to specifically "change" yourself. Yes you will change as you become a runner, but do it because its fun and worthwhile (yea I know what you'll be thinking when running that first 5K about mile 2 - sure fun and worthwhile I'm gonna strangle that guy on the DisBoards - trust me on this one, make it to the finish line and walk around for a few minutes after that - then about an hour later remember what I said). And dont tie running progress to weight loss, sure you can hop on a scale, but running goals are much more steady and sure, while weightloss can vary a few pounds in a day
3-Find a Friend. This is the ultimate motivation, it will make those hours and miles melt away. I have a great friend I run with as often as I can. Sadly that means once every other week or so, but sometimes we'll end up getting back to the cars and be lkie hmm, where'd the time go. You'll find yourself planning events and evenings centered around a run, we often do the run and happy hour thing (yes we shower in between at the gym). There are lots of running groups all over, any runner worth his salt will never look down on someone just starting to run. We all look like total fools at some point in our lives when we laced up those shoes and hit the pavement. Don't think you're any different. And remember this 3 years from now when you're cruising by someone just starting out, a couple quick words of encouragement or a wave can go quite a long way.
4-Be careful - one of the biggest mistakes a new runner can make is too much too fast too soon. I'd find a Couch 2 5K program and follow it. You're gonna find yourself wanting to go harder or faster, but for the first several weeks (at least to your first 5k) stick with it. You don't want to hurt yourself
5-Get the right gear - running clothes are half the fun. Collecting shirts from races is easily one of my favorite parts, love wearing the shirt (sadly I still havent found a reason to wear my disney marathon shirt, it was too cold this year in disney to wear it and i haven't done any races that have expos). Make sure you get a good set of shoes. And I would recommend running shorts or some other athletic shorts (probably not basketball or really long ones, chaffing is no fun). Technical fabrics are nice for shirts, but regular t-shirts will suffice. You dont need to drop a few hundred bucks, but get yourself some stuff.
6-Sign up early - book that half marathon now, start planning your vacation, get excited about it. But don't live in the future too much, enjoy the experiences now.
7-Get into the culture - running has almost a cult like following. You obviously dont need to be a fanatic, but see what all of us crazy people are crazy about. You might be surprised how fun it can be.