Tetris stacking

Premise
This article will deal with the the skill of stacking for many consecutive tetrises. It will be biased towards SRS/guideline games and will mostly apply towards slow gravity. It is a work in progress. Stacking for tetris is a useful skill in games that reward Back-to-Back tetrises, or do not reward t-spins. There is an argument to be made that pure tetrising is more elegant than other methods that involves lesser clears or t-spins. see for in-depth discussion.

Advanced techniques must be learnt through experience, and cannot be feasibly taught.

Basics

 * Stack flat, but not too flat, to allow for S and Z tetrominoes. Having a flat field will allow a player to rotate less, which saves time. A player will also have more placement opportunities. The even field will allow a player to think less which results in faster reaction times.
 * In SRS, leave the column on the far right open to tetris in, as pieces are biased towards the left. You will save a few translations because they will move a smaller distance.
 * Try not to build empty columns greater than 2 cells deep, as this will require an I tetromino that can be better used to tetris. However, a tetris requires 10 pieces, so for roughly every 2nd tetris, you have an I block to spare if you are using the 7-bag randomizer.
 * If hold piece option is available, make sure to keep an I in reserve to compensate for inconsistent stacking. Sometimes, a player is forced to create 3 cell deep empty columns that can only be fixed by an I tetromino. However, don't fall into the trap of stubbornly saving the I piece if doing so prevents you from stacking optimally.
 * Don't waste an I if another tetromino fits better. Use an I when stacking only to avoid future complications or at the beginning of a game. Don't forget that an I can be placed anywhere on the field due to its vertical orientation.
 * In singleplayer, try not to tetris if an I tetromino is not in reserve. Hold the I, stack more, and wait for the next I to come. Doing so will give a player more room for inconsistent stacking. Try not to tetris often from switching an I out of the hold box because it wastes a frame.
 * Avoid situations that force a player to soft drop. At the beginning of a game, avoid situations that force a player to soft drop more than once.

Much must be learnt from experience, and you will quickly see what pieces when placed in certain positions compromise your future stacking. When this happens, stop and examine the playfield, and determine the best position. Analyze your playing to better yourself.

Situational

 * Use a T to convert an S/Z field position into a Z/S.


 * Eliminate step pyramid structures with a T. Avoid fixing such situations with S and Z, which often leads to castle structures.


 * Eliminate castle structures with a T depending on your preview.
 * Avoid placing a J upright towards the left wall if you don't expect another J to appear soon. The same idea applies to L tetrominoes, either at a wall or at the edge (unless when skimming).


 * When dealing with a two-deep hole, make room for both J and L instead of blocking one off.
 * When having two open columns, deal with it as soon as possible. Over stacking will make things worse by having to wait on even more Is.


 * Remember that Random Generator deals a uniform distribution of pieces over the short run. Stack so not to require a duplicate piece, since chances are you may need to wait longer on that same piece than another one, having just used it.


 * Keep in mind that T-indents can be used to accomodate both S and Z tetrominoes. Don't rush to fill up the indent with a T if you see a barrage of back to back S and Z tetrominoes coming along.


 * Don't use S or Z tetrominoes to fix 3-celled pyramids unless you have an extra I handy. Opt for a T and L/J combination.