Try
to leave places where each type of shape
can be placed without creating a "hole" in
your wall. For example, try to make sure
you always leave a "flat" area
at least two columns wide, to make a safe
landing place for the two-by-two shape.
Since you get more points for removing
multiple rows at a time, try to fill
in only nine rows, leaving a narrow gap
that you can fill in with the long, narrow
shape (the one-by-four shape). This is
the only way to remove four rows with
one shape, which is your best scoring
opportunity. Of course, this is a high-risk
strategy, and is best-employed early
in the game when the speed of the shapes
is still pretty slow!
Since shapes drop from the center of
the playing area, try to fill up the
left and right sides during times when
everything is under control, so that
if you get into a crunch, you won't need
as many keystrokes to get a given shape
into its proper spot.