Here’s a quick run down (choose one or combine several, mix up the order, have fun):
1) Buy, borrow or build a dinghy sailor, teach yourself to sail in protected waters by reading and trial and error. (I did this many years ago.)
2) Take a dinghy sailing class. (I did this in Laser IIs).
3) Be crew in other people’s dinghy or keel boats.
4) Take a keel boat sailing class. (I did this in Santana 20s).
5) Join a club and sail their boats, gradually moving up in size as you’re comfortable.
6) Get bare boat certified and charter a suitable sized boat for a week or more.
7) Buy your own 27, 30, 34, whatever boat and start learning how to care for as well as sail.
8) Race as crew on another’s boat. (Could be done very early.)
9) Race as captain on your own boat, or a borrowed one.
10) Decide what you like best, and stick with it. Grow with experience.
Don’t underestimate the benefits of starting small (like a dinghy or small keel boat). Most importantly, do it until it’s not fun anymore.