TL;DR: The friend zone begins with failure to escalate.

Today a HB7.5 female relative of mine blabbed at length about all the male interest she is receiving, how hard her life is that she has to fend off suitors all day. Humblebragging. One of these males has been orbiting her for eight years. They met in high school and he imagined that by being in her life she would grow to like him with time, thus he friend zoned himself by failing to escalate sexually. The latest from him to her was an invite to an expensive dinner during which she does not expect him to deviate from his ineffective enchantments that rely heavily on of small talk and safe dry jokes while he waits for the natural phenomenon of osmosis to transmit desire to her. You could feel dry pussy rustle with boredom as she envisioned the date and tried to rescue excitement from the menu.

Another suitor basically threw himself at her feet along with the premature offer of a house and a car. She strongly suspects she would not be happy with him.

Another one - the one who excites her most - does not have much going for him in terms of career prospects, fame, wealth, compared to the others. But he takes every opportunity to impregnate her mind with sexual thoughts. She presents herself as a Miss Goody-Two-Shoes but he wreaks havoc on her daydreams and her eyes light up when she talks about him to the extent that she must cross her legs tightly because of the very real threat of him fucking her from inside her own head. We all know what's likely to happen; she'll probably marry one of the other guys for their stuff and commitment, but this casanova will get the milk for free.

Moral of the story: ESCALATE SEXUALLY or go home

As a man it is up to you to escalate; she most certainly will not.

Many women want to escalate, but believe that if they do you will think there is something wrong with them. "What will people say/think if I initiate things?" is woman's #1 worry. Relieve them of that burden and reap the rewards.

Don't worry about offending her. Let her worry about that. Ironically, the less you seem to care about consciously trying to impress her the better of an impression you'll make deep inside.

With failure to escalate comfort tests will multiply as you continue to hang around without pulling the trigger and she starts getting ideas to use you for what you are worth, which excludes sex. And you will fail all these comfort tests if you persist like that.

Escalate like you mean it, you can't half-ass it, like she frowns while you are mid-sentence and your mental alarm clocks all scream and all your warning signals flash "BAIL OUT!" and you fold your tail and retreat. Once you are in resolve to stick to the plan to the bitter end, with adjustments for calibration, but a chickenhearted retreat does more harm than never initiating the escalation in the first place.

The more you escalate with women the better at it you become.

There's my two cents. Flesh out escalation techniques in the comments please. I'm just here theorizing.