Your diet is the most important thing to think about. You can keep eating unhealthy things and working out and maybe you'll lose weight, but being skinny doesn't always mean you're healthy and it might make it harder to keep the pounds off.
(That's not meant for anyone to take offense to!
I lost a lot of weight a little more than a year ago by being active and eating well, and I still do. I work at a daycare where I'm constantly moving with energetic kids and I eat my fruits and veggies everyday, while avoiding junk foods.
I don't advise you go on a strict diet, they're not fun! It might stress you out more if you're constantly worrying about how many calories and cards and grams of sugar and sodium you've had.
The biggest step you can do is start eating more fruits/vegetables and drink more water. If you can't drink your full 8 glasses a day then aim for about 3-4 at first. The more you substitute water for juices and sodas, the less you'll find that you crave them. The same goes for junk foods.
There's a little fitspiration picture I always see floating around on tumblr that gives good advice: Healthy weight loss/lifestyles are 80% kitchen and 20% exercise.
But don't think that means you can't enjoy yourself everyone once in a while! I still eat cookies or pizza or hamburgers every now and then, just not nearly as much as I once did.