1.) Start tracking your intake/calories (myfitnesspal app).
::Track for 2 weeks, no other changes; during this time, also start listening to weight loss podcasts to stay motivated. I recommend "cut the fat"::
2.) Take stock of your intake and identify low hanging fruit - high calorie stuff that you can easily cut or sub out for lighter options.
:::Goal is to eliminate 500 calories per day. It's actually not that hard once you realize just how many calories are in certain foods. For example, if I normally eat a street vendor pretzel, that's about 400 calories right there. Sub that out for popcorn and you net out about 250. If you normally have a soda with that, sub it out with a water. Boom. That's practically 500 calories. Another big one is bacon -- sub out with Canadian bacon and save 1/2 the calories...
3.) Don't make any other changes and simply wait. You'll lose about 1-2 pounds/week (even more, early on).
4.) When you feel your cravings have stabilized, go ahead and find more low hanging fruit to attack.
5.) Once you lose about 10 pounds, introduce walking during your lunch break. By now, you will be feeling much better physically and mentally. Start very small - quarter mile, half a mile, etc. To make it fun, "reward" yourself by buying yourself a nicer pair of sneakers to keep at your desk.
6.) Every month, evaluate your progress -- if you've backslid, no worries -- just keep attacking the low hanging fruit. If you're ready for more (intake or exercise), go ahead but do so very slowly.
The key to this entire plan: DO NOT MAKE DRASTIC CHANGES -- YOU WILL RELAPSE!