Ways to practice and understand different accents in English.
One challenge in learning any language is the variety of accents that speakers have. Even when you can understand the "standard" version of the language quite well, you can have trouble understanding any non-standard accent. For this reason, it is advisable to "shop around"—deliberately expose yourself to a variety of accents, so you can gradually learn to understand the full range of pronunciations you will encounter in the real world.
Accents vary in strength, of course. Among both native and non-native speakers, you will always find some people with extremely mild accents. It's best, if you can, to look for accents that are slightly stronger, so you can see the typical features of that accent more clearly. (For this reason, it is sometimes best to avoid the news programmes of national broadcasters, which are often in an almost artificially accent-free, neutral English.)
It's a good idea to work hard on one sample recording of each accent first – say, ten to thirty minutes. Keep listening until you can understand it completely. You can even try copying the accent aloud. This will help you remember and understand the accent better.
Don't exclude an accent just because you think you will never encounter it or need to understand it. A part of the purpose of this exercise is to get a better feeling for the range of possible accents in English. For this purpose, listening to "more unusual" native speaker accents—Scottish, South African, Indian, Jamaican, North English etc.—is probably more useful than listening to the "standard" accents.
If you know you are going to have to travel to a certain place, it is probably a good idea to try and find some material that will help you get used to the accent of the people there before you go.
There are a number of ways you can practice listening to different accents. (Click on the links to see a lists of resources to get you started.)