For me, noun declension learning is one part "learning in context" and one part rote learning.
With regard to the former, one simply needs to read a lot (listening isn't quite as effective, as you can't see the spelling of the word being said).
As for the latter, I like to "write out" my noun declensions -- the physical act of writing helps drive the matter into my brain.
Here's a set of noun declension sheets I made up for Munster nouns:
http://www.gaeilge.org/munster/MunsterNounDeclension.html If you're going to go to the bother of writing things out, why not do so in an orderly way? These sheets have blanks for every type of noun variation (nom./acc., genitive, vocative, dative) within each declension.