How does a trend start?
How is a trend born?
Accumulation and distribution?
Well, you're asking The Million Dollar crystal ball question there

-- and no one in the world owns a crystal ball,
There are alot of fakeout wildcards too thrown into the mix to weed out the joker trader masses, -- I'm kind of loosely quoting Billy Ray Valentine here from the movie Trading Places.
Forget about timing, just aim for closely timing. You can make a very handsome killing in the market by just carving out your middle portion...as another person pointed out with his roast beef example,
The simplest answer I can give you...think of, or envision,
Mountains...when you see the top tip...tipping...that's generally, safely, a new backwards trend,
Or think of the bottom of the ocean floor as well starting to slope upwards,