80/20 Martial Arts

Most people are familiar with  the Pareto Principle -
... named after economist Vilfredo Pareto, specifies that 80 percent of consequences come from 20 percent of the causes, or an unequal relationship between inputs and outputs. This principle serves as a general reminder that the relationship between inputs and outputs is not balanced. The Pareto Principle is also known as the Pareto Rule or the 80/20 Rule. 

Certainly, this rule also holds true in the martial arts. 80% of all techniques used in actual combat stem from 20% of all techniques that are out there. The Rifleman also points out to his students that the 80/20 rule applies to the remaining 20%, as well.

In other words, a select group of techniques accounts for 80% of all used in combat. And the second most common group of techniques comprises 16% of all techniques used in combat. Combined, these first-tier and second-tier techniques comprise 96% of all techniques used in actual combat.

Let's take a look at a quick list of those first-tier and second-tier techniques in Jiu-Jitsu:

Takedowns
First-tier - double Leg Takedown, Single Leg Takedown.
Second-tier - body fold takedown, leg sweeps, rear takedown.

Positions
First-tier - standing, Mount, guard, side, back.
Second-tier - half guard, modified mount, headlocks, turtle.

Submissions
First-tier - RNC, Guillotine choke, triangle choke, straight arm lock, Americana, Kimura.
Second-tier - arm triangle, footlocks, cross chokes, collar chokes.

Escapes
Escapes are a slightly different animal - a good Jiu Jitsu practitioner needs to have a couple of tried-and-true escapes from each position.
Mount - hip lift escape and shrimp escape.
Side - shrimp escape and going to knees.
Back - unhooking a leg and pulling on the legs.
Headlock - frame escapes and going to knees.
Turtle - sit out, stand up, and go to guard.
Guard passing - knee slides and stacking.

Misc.
Throw in a few guard sweeps, positional stabilization, transitions, and some situational principles, and you will be well on your way to becoming a complete grappler.