In the section titled Hand Rankings in Part One of their book Hold Em Poker For Advanced Players, David Sklansky and Mason Malmuth present a set of groups for the starting hands, i.e. the hole or pocket cards dealt the player by the dealer. To quote:

The reason for this is that most of the hands in each grouping can be played roughly the same before the flop in many, but not all, situations.

The Rest of the Top 20 Hold'em Hands. The top 10 best starting hands in Hold’em are a good starting point for poker players but every potential starting hand can be ranked all the way down to the lowly 7-2 off suit, which only has a 4% chance of winning versus random cards.

• The table is a general ranking of hands in Texas Hold'em. The Sklansky and Malmuth starting hands table groups together certain hands in Texas Hold'em based on their strength. Starting with the strongest set of hands that you can be dealt in group 1, the hands get progressively weaker working down the table until the virtually unplayable hands.
• In traditional Texas Hold’em this is the worst starting hand, and almost completely unplayable. Well, as you can probably work out yourself quite easily, in Six Plus the equivalent hand is J 6 offsuit, which, let’s be honest, would rarely be played even in our normal game!

Furthermore:

These rankings reflect not only which group each starting hand belongs to, but its approximate order in that group as well. In reality, it’s usually only necessary to know in which group a starting hand belongs.

And, finally:

Texas Holdem Starting Hand Rankings

If you are new to hold ’em we feel it is very important to memorize these groupings. There is no way around this, and the tables make the task much easier. Once the tables are memorized, this system will facilitate applying many of the concepts that follow.

As it turns out, I memorized the grouping lists and not the tables that follow them, and the reason why I delayed starting this blog was that it took me from mid-January till last Friday 10th April to complete the task of memorization. If I am entirely honest, I did not have confidence that I would be up to the task, and I wanted to take it step by step, and ensure I had committed each group to memory before moving on to the next group.

To further quote them:

The rankings are as follows, with an “s” indicating suited and an “x” indicating a small card. Note that a 10 is represented as “T.” Also, if no “s” appears, then the hand is not suited. (These notations will be used throughout this book.)

I replicate the groups and ranks here, as I have committed them to memory. Believe it or not!

How did I memorize this list? I did this through rote memorization, before I discovered the memory palace, but with the added twist of using the Phonetic Alphabet to help commit the groups to memory. So, for example, I memorized Group 1, by reciting the hands as follow:

Group 1: Alfa-Alfa, Kilo-Kilo, Quebec-Quebec, Juliett-Juliett, Alfa-Kilo-Sierra

and finally, as another example, I memorized Group 4, by reciting the hands as follows:

Group 4: Tango-Nine-Sierra, Kilo-Quebec, Eight-Eight, Quebec-Tango-Sierra, Nine-Eight-Sierra, Juliett-Nine-Sierra, Alfa-Juliett, Kilo-Tango-Sierra.

Texas Hold'em Starting Hand Rankings

So, if you memorize the phonetic alphabet, it becomes easier to memorize the lists as they appear in the text.

Texas Hold'em Starting Hand Rankings Chart

Observe that you are memorizing 5+5+6+8+11+10+12+15=72 useful hands, grouped by ranking. Now, there are 13×13=169 card combinations, and 1,326 combinations if you consider all suits as separately counted.