Lots of people get out of shape, don't think about it, and then one day hit rock bottom or have a realization and go crazy to get into shape.
I'm not sure that's the best way to go about it.
I was pretty significantly injured in March (described here), and my fitness probably hit a low point in May. Now it's interesting - I actually haven't been on any sort of hardcore program since then, but I see my fitness levels improving.
I started working in movement and motion into every day. I tried to go for a walk, at least 15 minutes but ideally an hour every single day. No matter how busy you are, you could find time to do this.
I multi-task the walk. At the very least, I listen to an audiobook. This seven hours of walking time each week means I get through lots of audiobooks, which is great. I'm learning every day.
When I run errands, I try to walk instead of taking a taxi if I'm not in business clothing. After reading Bruce Lee's book, I started taking the stairs. ("Bruce Lee Took the Stairs")
I haven't gone on any crazy fasting or binging with my diet. I've gradually started eating more fruits and vegetables, and gradually cut down sugar. I do some situps most days, and pushups or pullups sometimes. This is something anyone could do - start with 5 situps. Anyone could do 5. Then build up.
I stretch every day. I started my stretches with a program I got from a physical therapist for my legs, but gradually added in arms, torso, neck, and back. It's good, I really like stretching. I feel a lot healthier when I'm stretching, and it's own sort of pleasure.
At some point, I'll be settled in again and I might get a gym membership, or take up CrossFit or something. But it's not entirely necessary. If you're busy, it doesn't have to be an all or nothing proposition - for a lot of people, they destroy their health until one day they get into a hardcore regime. Problem is, it's easy to fall off a hardcore regime if you're busy.
So, how about you stop waiting, and start adding a little more fitness into your life? A 15 minute walk, 5 situps, or try to eat vegetables at least once per day? Start tracking how often you eat sweets, and scale that down? Start taking the stairs instead of the elevator?
It's pretty amazing what the human body can do after a short period of hardcore training. But even if you never do some hardcore training, why not take some little measures so that your health will be better in six months than it's going to be if you don't? If you keep making little changes to your health, diet, move around, stretch, strengthen - just little tiny easy changes - you're going to have exceptional health in a couple years.
I know that's not as exciting on first glance as whatever the newest "ultimate hardcore get in shape in only 30 days" fad is, but consider - it's basically free. Add in 5, 10, 15 minutes of motion to your life. Swap one piece of cake each week for a fruit plate. Order a side order of vegetables with whatever else you eat. Take the stairs once this week. Little changes like this don't tax you, they're not particular hard, and they do add up. Fast, hardcore fitness might be good. But regardless of how hardcore you want to be, why not start slowly adding little improvements right now? Six-months-from-now you will be very grateful to today-you if you do this.