first, you must memorize basic strategy and it must become second nature.
then you need to learn how to add the point values of all the cards that you see. using "hi/lo" as an example system, the 2-6 cards are valued at +1, and the 10-value cards and aces are counted as -1. the 7, 8, and 9 are neutral in this system.
to learn how to keep the running count, get a deck of cards and flip the cards over one at a time and keep the running count. if the cards come out 8,q,2,2,6,3,a,7 then we would count 0, -1, 0, +1, +2, +3, +2, +2. after you are done 