while it is possible to add muscle and lose fat at the same time, its not optimal. you have to determine what your goals are for right now, for a year from now, for 5 years from now, etc and then go in that direction. if you want to make any sort of real muscle gains, you need a caloric surplus. you can fine tune that surplus all you want, but typically the side effect will still be some fat gain. if you want to lose fat, you need a caloric defecit.
your exercise plan may vary. some people lift heavy all the time. some people only do bodyweight work. some people use more of a bodybuilding styled workout plan. again, what are your goals?
personally, i like to add muscle over the winter time. i'm hidden under long sleeved shirts and sweaters for months at a time. so i do most of my heavy lifting in the fall and winter. i eat in a caloric surplus. i add a few lbs of muscle and a few lbs of fat. for the spring and summer, i want to lose fat, so i shift the focus of my workouts, and clean up the excess calories. the extra few lbs of fat come off and i look good on the beach.
I have a lot of hard miles on my body from before I realized I'm not 100% invulnerable. Now I just think I'm 75% invulnerable. -Mr. Anthony