It would be better to say, "How can I improve my listening skills?' Retaining your original structure: How can I be excellent AT listening? That works, but not as well. Most people would want you to change it to "How can I become excellent at listening?" or something like that. Well, you could listen to something with a script in front of you, so that you could read the words at the same time you could practise and practise and practise you could engage conversation with a language exchange partner you could hire an English teacher who will talk clearly at your speed, and repeat things that you don't understand That's all that comes to me at present.

I often have same question.I'm also learning E and I realized that you exercise every day will bring unexpected results.we need to persevere

listen everyday, be obsess with every word you hear. Don't go to any class if it is not necessary. I adopt English accent by watching movies and listening to music from the first day i learned English. Since American accent is really easy to hear so you should try it first. If you have gotten the hang of it, you can try more accents. it is the method to practice both listening and speaking skills at once.