To memorize numbers 0-9 they can easily be associated to things that the numbers look like. Thus,
0 = football 5 = clothes hanger
1 = telephone pole(many others) 6 = elephant trunk
2 = swan 7 = boomerang
3 = handcuffs 8 = snowman
4 = sailboat 9 = basketball hoop
Two digit numbers are memorized in a more complex way (very similar to the Major System)
0 = O 5 = E
1 = A 6 = S
2 = B 7 = G
3 = C 8 = H
4 = D 9 = N
Each two digit number 10-99 gets a number combination. A person, action and object is given to each two-digit number. The letter combination of each number should somehow remind you of the person, initials perhaps or any other way.
To memorize a two-digit number, imagine the person doing his/her action to a location where you want the number to be associated. For a three-digit number, do the same for the two-but incorporate the individual image and place them in a relevant location. For a complex system of numbers 4+ you simply alternate between person action person (Darth Vader playing chess with President Obama). This is really similar to the PAO system, except in the PAO system the six digits are represented by one person one action and one object. In the Dominic System, the six digits are represented by two people and one action.
According to Dominic, it is far easier to memorize a person than an object, so he says his system is far better.