When people say they want to work on their accent, they usually say that people can’t understand them. A lot of times, what happens is that the characteristics of your native language might seep into your new language so much that it can be difficult for someone who is unfamiliar with those language patterns to understand your spoken words.
If fact, in Spain, the guy at the cafe refused to serve me coffee unless I said the word the way they said it. (Not cor-TA-doh, it’s cor-TAO). I think it was because even though I knew the word, my American English characteristics were so strong that what he heard wasn’t me ordering coffee in Spanish- it was a combination of nonsense American-sounding syllables. If I were to go to England, or watch British soap operas on TV, I might encounter a similar situation. Even though I speak English, the characteristics of the English I would hear in England would take some getting used to. For English learners, compound that with new vocabulary and regional colloquialisms, and you have a perfect storm.
Accents can be created by maneuvering your tongue, lip, and jaw. Accents, however, aren’t just how our mouths are positioned. They represent, to a large degree, our familial and regional heritage. People take pride in their accents because they represent where they’re from and who their parents are. Culture is very important, and should not be overlooked in the discussion of accents. Some places might be perceived as better than others, which is why some accents might be perceived as superior to others. There are no superior accents; only perceptions of superior accents exist.
Rather than learning an accent for its perceived superiority, start with these questions:
When you want to speak English well enough to be understood, where will you be? What are the sound characteristics of the consonants and vowels of that region? These characteristics vary from place to place. What about these sounds are difficult for you to say (based on your native language). If you work on your mouth position for these sounds, will people understand you?
Ultimately, your goal is to communicate to get your needs met. My tips for starting on accent improvement are in the beginning stages, (1) refrain from using too many regional expressions and (2) keep your word choice and sentence structure simple.