We will cover four stages of kechari here (see Image for sketches), all pertaining to the location of the tip of the tongue:
Stage 1 - To the point on the roof of the mouth where the hard and soft palates meet. This is the line of demarcation that must be crossed before stage 2 can be entertained.
Stage 2 - Behind the soft palate and up to the nasal septum. It is a short trip, but a momentous one. Initially this is done with help from a finger pushing back under the tongue, going to the left or right side of the soft palate where entry is easiest. This may require "breaking the hymen" of the membrane under the tongue. See below for more on this.
Stage 3 - Gradually working to the top of the nasal pharynx and septum. This takes us to the bony structure containing the pituitary gland.
Stage 4 - Entering the nasal passages from inside and moving upward beyond the top of the pharynx toward the point between the eyebrows. It is not as far for the tongue to go as it seems. Put your thumb on the hinge of your jaw and put your index finger at the tip of your tongue extended straight out. Then pivot the fixed length to your index finger up on your thumb to the point between your eyebrows. See? It is not so far for the tongue to go straight up from its root.