I found a basic answer on my question over here:
Try to go out waiting for multiple
tiles (not just one). Imagine that you
have three complete sets and two
pairs. Imagine that one pair is 2
Bams, and you draw a 3 Bam from the
wall -- which tile do you discard now?
In this situation, many experienced
players will discard a 2 Bam, keeping
2-3. A two-way incomplete chow call is
better than a two-pair call.
shape the hand into calling patterns
that give you multiple chances to win,
such as the following:
Tiles in hand Call for
22234 RR 25 R
Highly skilled players of
un-American mah-jongg (since American
style alone does not use "chows") know
these patterns by heart. More complex
call shapes are mostly extensions of
these. Although the American game does
not use chows, the strategy of having
a multiple-tile call still applies to
that game as well.
Of special interest
is the complexity of the pure hand. If
you're working on a pure hand, it can
often be difficult to tell what all
the tiles are that can complete the
hand. For instance:
1-2-3-4-5-5-5-6-6-6-7-8-9 (5 chances);
chances); 2-3-4-4-4-5-5-5-6-6-6-7-8 (7
chances); and of course
1-1-1-2-3-4-5-6-7-8-9-9-9 (9 chances).
Edit: Additional links with a lot more waits
Especially the latter is, from my beginner eyes, insanely exhaustive.