I'll take a shot at it.

Here's a symmetrical gal not ready to flower.
Note that the branches n fans are opposite each other on the main stem.
Attachment 283499
(FYI!
This gal is about 80% indica.
Pure Indica has even fatter fans.)

Here the branches are just starting to grow alternately on this young stud.

Attachment 283501

Here's a bouncing baby boy gone alternate.
A branch on one side, then some distance, then a branch on the other side
I flowered him a little early because he just looked like a boy from day one.

Attachment 283500

Here's an older girl.
Branch, fanleaf, and an aging female pre-flower all on one side of the stem.
About the time your pre-flowers reach this size, is when you need to begin watching the trich heads for ambering.
Attachment 283498
Bottom line, if the fans/branches align at the same position on both sides of the main stem, it's time to wait.
When they start to alternate, and, they are half the height you want at finish, flower them.

If that's not clear, you are out of luck and will just have to do a lot of reading.

Aloha,

Wee 'zard