Alberto_Italiano

For unknown terms, google.

The position (asana) is not really relevant: whatever position best suits you for meditation or zazen, is already an asana Patanjali says.
You may even just lay.

Meditation differs from zazen inasmuch as with meditation you may choose a subject to focus upon (inclusive of an emotion).

Zazen, technically means that you stop your mind - that is, you try not to think. At that point position is not relevant, you will find already that controlling your mind is nearly impossibile, thoughts will keep popping.

It is said that if
1) you manage to do prolonged zazen without actual thoughts popping in
2) you manage to do that while in action
you would be (I quote from Takuan Soho) "unbeatable". However don't count on that - it is said also that one in several millions may succeed in being in full zazen whilst in action.

If you do zazen long enough, say months, you may add breathing exercises (though then it would be pranayama more than zazen, which implies not thinking even about breathing).

If you enter in dhyanas, it is reported you may spend a whole day there and not realize it.

In rare cases, you may experience stuff akin to OBE, it is said.

All signs like shivering, mental lights, physical vibrations, feeling circulation and pulse are normal. If you go on for a few months, you may get a taste about why they spoke about chakras, particularly abdomen and neck. If you start feeling chakras, you may get scared. If you don't get scared, I have no idea what happens next because I did.

ps: other phenomen I stumbled into: thoughts start falling in you: as if they were weights. Since you don't follow them anymore, they just "happen" but you let them go so you have the impression they have been flung at you. At times, you may experience a very frightening thing (at least to me): fully composed and meaningful sentences may start crossing your mind as arrows cast from who knows were - they swwoooooosh right in front of you, with a meaning.