More on the theory and background has been written by others.
Here are some practical notes for my own personal usage.
If you need to build flash card to cover your own research area, there are two contenders, Anki and Mnemosyne. I use the former because it has the convenient features of testing your flashcards on the iphone, but they are both open-source-ish.
Some of the best data on this phenomenon come from studies of Japanese adults learning to hear the difference between r and l. Why the Japanese? For one, because the r-versus-l problem is notorious; Japanese speakers tend to do little better than chance when attempting to tell their rocks from their locks. Second, they know they have this difficulty, and many will happily volunteer to come into a research laboratory --- whereas English speakers do not care much about learning the difference between Hindi's four nearly identical-sounding d's.
With a handful of recordings […] (freely accessible through Web sites such as Rhinospike and Forvo) and with testing software such as Anki, you can build powerful ear-training tools for yourself. These are tools that, after just a few hours of use, will make foreign words easier to hear and easier to remember, and they may give you the edge you need to finally learn the languages you've always wanted to learn.
More on Minimal Pair Tests