Home keys are the four keys on which your typing fingers of each hand rest in a state of readiness. For the left side of a standard QWERTY keyboard, the home keys are "A," "S," "D" and "F." Your left pinkie rests on the "A," your left ring finger on the "S," your left middle finger on the "D" and your left pointer on the "F." The first and easiest drills are to press the keys, forming either a series of meaningless letters or simple words. For example, you should type "ASDFFDSA" several times to form the memory muscle of your fingers on the keys. You can then move on to singling out "A" and "S," as they are associated with your least dominant fingers. From there, move to typing simple words such as "SAD," "AS," "FAD" and "ADS" repeatedly.
Based on their position on the home keys, each of your fingers is responsible for several other letters on the left side of the keyboard. Your pinkie is responsible for uncommonly used letters on the edge such as "Q" and "Z," your ring finger for "W" and "X." Your middle finger is only responsible for "E." Your pointer finger, as the dominant finger on your hand, handles "R," "T," "G," "C," "V" and "B." By isolating each finger, you can practice the transitions from the home key to each finger's letters. For example, you could repeatedly type "QAZZAQ" or "WSXXSW" to establish the memory muscle for moving from the home key to the outlying keys and back.
Upon establishing both the home and the range of each finger, you can move on to typing two-level and three-level, one-handed and left-sided words, for example, "WERE," "DRAT," "BASE," "SAW," "AXE" and "FAZE." In typing these words, you establish the muscle memory of both moving individual fingers to and from the home keys, as well as the interrelationship of different left-handed fingers moving in concert.
The final drill for improving your typing skills on the left side of a QWERTY keyboard is to type complete ideas with nothing but your left hand; you can't type complete sentences yet because the period is the purview of your right ring finger. For example, "TED SAW A BEAR," "FRED BEAT A BAD GRADE" and "BRAVE BRAD SAVED A SAD TRACE" string together left-handed words. Though the ideas are nonsensical, combining two- and three-level words together into such groupings establishes the memory muscle necessary to be an expert typist.