* To improve your pronunciation, first practice the BASIC SOUNDS of English. The 26 letters of the English alphabet make up 44 basic sounds ...
(think how the "a" sounds different in each word in "Father ate an apple"). You can practice them with 44 excellent videos on this BBC site. Don't worry about the strange symbols, just practice them one by one.
* Once you know the basic sounds, compare and practice SIMILAR SOUNDS (like t/th, r/l) with shiporsheep audios or videos, or this series of EngVid pronunciation videos.
* Other important factors for a clear and natural pronunciation are stress (some words and syllables spoken longer and louder than others), intonation (voice going up or down) and linking (words together). You can find a small selection of practice videos on podcastsinenglish, but it is a much better idea to COPY THE PRONUNCIATION of the videos and audio clips with script you use to Improve your English Listening.
