Folding Procedure (1)
Full folding has a clear procedure.
If you fold properly and follow the procedure, your deal-in rate will drop sharply.
The Basic Idea of Full Folding
Discard the safer tiles first.
That is the basic rule.
Do not worry about breaking up your hand.
So as long as you still have:
- genbutsu
- completely safe tiles such as honor tiles with three copies already visible on the table
you should discard those first.
The important point is to discard the tiles that are guaranteed to pass first.
During a single turn, more genbutsu may appear.
Someone else may deal in, or the riichi player may tsumo before you have to discard again.
If you still have safe tiles in hand, but instead discard something that merely "looks like it might pass,"
then from a defensive point of view, that is a loss.
Priority Among Genbutsu
Even when you have multiple genbutsu, there is still an order.
The rule is: discard the genbutsu that will become more dangerous later first.
Example
This hand is already badly scattered.
Trying to fight the dealer's riichi from here would be almost suicidal.
Your current safe tiles are:
It is fine to cut either 
or 
first,
but cutting 
first is a mistake in order.
If another player now declares chase riichi, you could suddenly be left with no safe tiles at all.
And in this diagram, the player below has already started cutting dangerous non-suji tiles,
so another riichi here would not be surprising at all.
That means this is the kind of position where you should not hesitate to discard and first.
Theory
When you have multiple genbutsu, save the tiles that are safe against everyone.
Next time, we will continue with the case where you no longer have any safe tiles in hand.
Original Japanese page: http://beginners.biz/mamori/mamori06.html