In much the same way I treat active and passive participles, as I practice and read new things, I try to use the exhaustive definition of each correlative so that it sticks into my brain in a more rounded way. This is especially useful for the ti-, i-, ĉi-, neni- correlatives:
I read tial as "(for) that reason", ial as "(for) some reason", etc.
It also greatly helps (and this is a trick I learned from the Esperanto Duolingo Facebook group) to simply memorize a few key phrases that have easy meaning (this is especially useful for me when dealing with kial and kiel). Or just memorize one phrase between similar words (again, like kial and kiel).
My descriptive phrases:
"Kiel vi fartas?" (ok, so I know kiel is how, not why... kial is why.)
"Kia aŭto?" (what type of car?)
"Kies aŭto?" (whose car?)
Those, honestly, are the hard ones. -u and -o correlatives are very simple:
Use -u when referring to a person or one out of a list (most of the times, there is a noun attached to the correlative unless referring to a person).
Use -o when there is no way to attach a noun to the correlative.
Example: "Kio tablo?" is incorrect. Use "Kiu tablo?"