OMG do I ever know where you're coming from. There are so many articles - 20 minutes, 30 minutes, 40 minutes, an hour???
I personally feel that doing high intensity intervals is the best...but I like to MIX IT UP. Right now, I'm doing 3-4 cardio sessions a week along with a four day weight training split. 3 of those sessions are 25-30 minutes long - 3-5 minute warm up, intervals for around 20 minutes (or more if I can stand it!) - two minute 'jog' followed by a 1 minute all-out 'run' (generally on the elliptical which is my favorite machine) for 6 or 7 intervals, followed by a cooldown of about 5 minutes or so.
On Thursdays I don't lift at all - I do a 40-45 minute session which essentially is half moderate cardio, half intervals - 5 min warmup, 5 min moderate, 8 or more intervals, and then a 10 minute gradual cooldown.
And on Sundays, I do some moderate cardio - on nice days, that generally means going hillwalking with my sister.
As far as calories - I'm a HUGE believer in zig-zagging the calories - keeping your body guessing. If you eat the same amount every day, then your body becomes very resourceful at retaining its reserves at that amount of calories. Some days you might want to have a 1700 calorie day, other days drop it down to 1500 or so. Bodybuilder Tom Venuto is a HUGE believer in zig-zagging calories - check out the "Articles worth Reading" sticky in the Ladies who Lift forum for some really good articles and links on the topics of fat loss.
Of course, one thing to keep in mind is that we're ALL DIFFERENT. Unfortunately there IS no one way that works for EVERYONE - as we're all at different fitness and skill levels, and even individually as our fitness level improves, we need to tweak and try harder to get results. You've only been at this a month - have PATIENCE and be PERSISTENT in working towards your goals and you can't miss!