There are a couple of popular routes, as DB stated start small be consistant, exchange the crap you consume for a more balanced diet, its ok to eat chocolate, drink beer, but in moderation, a balanced healthy diet is not rocket science, some can stop consuming most unhealthy foods drinks etc, and only have a problem with certain items, usually chocolate, alcohol, chips or as we call them crisps, and the worst imo energy drinks, the likes of monster relentless etc, and the times of day they consume these products, with busy lives, skip breakfast, busy day at work, get home have tea, then sit in front of the idiot box watching sitcoms made for 3rd graders, drinking beer and snacking, not realising in the 4 hours they have been home from work, they have consumed 2000 calories, then go to bed.
The 2 ways you do this is either make small changes and be consistant, or make big changes for 6 days aweek then have a reward day, my advice would be the 1st, a good plan to go with the balanced diet and exercise would be, and its something I have done since the 1980's, after seeing it on a breakfast tv with mr motivator is the following:
Eat breakfast like a king
Eat lunch like a lord.
Eat tea like a porper.
No supper.
And most importantly drink 3 litres of water aday.
With consistancy and discipline the weight will fall off.