How to find ultimate good posture?

First, study some books about nutrition so you know how to eat right. Magnesium strengthens muscles, calms nerves, stops cramps, and fights infections. Get epsom salt. It is cheap, five bux for a year's supply. Put a dose in a glass with water to cover and stir until it dissolves. Fill the glass with lemonade and drink it. You can take it without the lemonade but you won't like the taste. Milk of magnesia is more expensive but nicer tasting and gentler laxative action. Your choice. You can also get magnesium pills for daily dosing.

When you sit, roll your hips forward so your spine is straightened. It takes a while to form a habit to sit this way. You will notice an immediate improvement in breathing and alertness. You can stay awake all day this way, as long as you don't slip into a slouch.