Although correct intonation (or the sound of the language rising and falling) is thought to be the most important part of accent reduction, correct pronunciation is also important. When the "p" and "t" sounds in English are produce properly, air comes from your mouth. Take a list of words beginning with, or including "p" or "t," light a match and place it in front of your mouth. Say each word, if the match flickers or goes out, you're on your way to reducing your accent. You can also try it with a piece of paper, trying to get it to move each to you say "p" or "t".
The "music" of English is one of the main things that separates native from non-native speakers. In general, the first noun in a sentence gets stressed the most in English. Intonation is also used to show contrast, new information, meaning, pronunciation and mood. Take the sentence "I didn't say he bought the car," and try saying it seven times. Each time place more stress on a different word and listen to how the meaning of the sentence changes. Then try the exercise again and add a phrase at the end that explains each meaning. For instance, if you stress "I," add " . . . someone else said it."
If English isn't your first language, chances are you don't have any experience making the "th" sound, unless you speak Castilian Spanish or Greek. When you make the "th" sound you should be able to see your tongue between your teeth when you check in a mirror. For extra practice, try saying this sentence: "I thought the thin stick on the path was thrown by the moth" while looking in the mirror. Your tongue should stick through your teeth eight times. If it doesn't, you're probably replacing the "th" sound with "d" or "t."
The International Phonetic Alphabet (IPA) is used in standard English dictionaries and provides a standard for correct pronunciation. The IPA chart has listings for every sound produced in the English language along with examples and can help you when you find a word that gives you trouble. Go through each example word, pronouncing it slowly until you get the correct sound. Eventually, try to incorporate the word into a sentence and practice reading newspapers or magazines