I believe what you are asking is, "how can I go from a set of categories to drawing a grid"? I will demonstrate how to do this in two ways.
Purpose of the logic-grid set up
First, let us establish the purpose of the logic grid. All categories intersect, but only once. This allows any information relating any categories to be marked down in a ...
There are many ways to go about this, but here is the easy grid way. This is a long detailed description for how to solve so someone else will probably beat me with a simpler method, but this one will work every time and becomes easy to do.
A step-by-step solution can look like this (I didn't see the solution at the link):
(Well, no spoilers since a solution is already given by the OP)
Let's enumerate the conditions for better referencing:
(1) B works in department M and earns more than 20,000.
(2) Person who is 28 years old works in department Q.
(3) 32 years old person earns at least 20,000.