So, I've been fat for most of my life, and I want to do something about it. People here that used to be fat, how did you get to where you are now?

exercise (start by walking if needed, progress to running/biking/yoga 3-6 days a week, strength training 2-4 days a week)
eat clean (lots of veggies, lean meat, fish) and in appropriate amounts
drink lots of water water, maybe some tea/coffee if you must (but don't add milk/sugar)

>>1
Exercise pulls you into shape. It's a myth that exercise can burn enough calories to make a difference in size/weight.
The only way to reduce weight is to change your diet. Just minimize the amount of fat, meat, sugar etc that you eat. Be aware that fruit is high in sugar. Go easy on it.
Smaller portions are easier if you use smaller crockery.
If you're in the US look out for high fructose corn syrup. Avoid it wherever you can.
Stopping eating while you're still hungry will shed pounds fast.

Dude go download this app, it's free, it's called "lose it" I'm sure there are other apps that do the same thing. You simply input what you eat daily and it tracks your calories. Seeing what you eat changes your perspective on shit. That and exercise will help. I lost 40 lbs a couple summers ago thanks to that app. Good luck