I'm certainly not a weight loss expert, nor am I anything close to an exercise guru. What I can tell you, however, is that I lost almost 50 lbs. last year over the course of about 2.5 months and I made only two basic changes to my lifestyle.
One, I started monitoring very closely what I was eating. As has been mentioned in this thread already, it matters a great deal what your daily caloric intake is. This is not to say that I started eating only "healthy" foods and gave up all junk food, etc. Not at all, in fact. I found very quickly that there were days when I was far under my daily caloric allottment, and there were days when I was over. The important part was that it all balanced out to a daily average.
Change two was exercising for 30 minutes a day, six days a week. For me, it was running. I actually followed a "couch-to-5k" routine, but I'm sure any 30-minute cardio workout would work. I have a full-time job and I'm in graduate school so free time is essentially non-existent in my life. But, 30-minute exercise routines at home (e.g., running) are perfectly doable and manageable and so I had no excuse.
Not gonna lie, the first three weeks or so of this new routine (monitoring what I ate and exercise) were horrible. I was tired all the time, and felt like I had less energy than before I started my new routine. I was also hot all the time, which I couldn't figure out for the life of me, being that it was January/February. But, I was determined to make this work and after about the fourth week, I started noticing that my clothes were too big and that I had more energy at weird times of the day when I ordinarily wouldn't (mid-day, for instance). I stuck with it and after about a total of about eight weeks, I had lost just about 50 lbs. It felt amazing to know that I accomplished what I set out to do and it felt even more amazing getting complements from loved ones and acquaintences alike about how great I looked. Now, just about a year later, I'm not exercising as frequently as I was previously but I'm still maintaining the weight loss. Even when I was hospitalized and put through two surgeries, I only gained about five pounds back. I'll be taking a break from school shortly and I can't wait to get back on the full exercise routine and hopefully lose another 20 lbs. or so.
Good luck to you, OP!!