it's not as complex as people think, or, it wasn't complex for me.
i was around 240lbs, so i decided i was sick of being a fat twat and decided to do something about it. i went on a diet where realistically i just counted my calories and created a deficit every day, while ensuring the food i was eating was balanced and healthy, of course i didn't do it every day, one day every week or two i allowed myself a treat, whether it took me over my calories or not, because life still goes on, and i don't ever plan on cutting them out of my life forever.
exercise is great as well, which when i started literally allowed the weight to drop off me. i've never had great metabolism, but it really helped.
i started around a year and a few months ago, only started going to the gym properly around 3 months ago and am now at 172lbs and thinking about slowing down soon because i'd rather not be too skinny. (bearing in mind i'm 6'2)
well, that's my input on it, i hope it helps!
(ps don't do an all liquid diet, i know two people who did it, lost an insane amount of weight in a short time, and then put it all back on when they started eating food again, even though the food they were eating was all vegetable based with some red meats, perhaps it may only work for a few types of people, but i don't think it's worth the risk.)