Congrats on getting started. I love calorie counting because I don't feel like I'm on a diet, I don't have any food that is off limits which is nice. It's all about eating in moderation and learning proper portion sizes.
With only 15 pounds to go my biggest advice to you is to be patient. I've read numerous times that it's healthiest for people with less than 20 pounds to do it at a pace of between 0.5-1.0 pound a week. Any faster and you could start messing up your metabolism/lose more muscle mass than fat. I'm currently losing about 0.5 pounds a week, I've got about 10-15 pounds to go, and I like it because I never feel deprived yet my number keeps dropping, even if it's slow.
I personally plan out my food but that's mainly my personality type. I like a plan for everything. I also find it really easy to follow though my breakfasts, dinners and snacks are usually identical. However when I first started losing weight I didn't plan it out, I just used an online calorie counter (myfitnesspal) and stopped eating when I got to my limit. After awhile I realized I needed to plan a bit better so I could have an after dinner snack.
To figure out what calorie level you should be at, I'd recommend this website:
http://scoobysworkshop.com/calorie-calculator/
It will probably give you an amount higher than you think but it's never failed me and it was recommended to me on MFP. As I said I lose .5 pound a week and don't exercise, eating just less than 1600 calories a day. When I was quite larger, 40+ pounds ago, I ate around 1650 a day and lost 1.5 pounds/week on average.
Good luck.