Learn the most common consonant sounds first. These are often the easiest to remember because they are transcribed using the usual English letters. Sounds such as m, n, p, b, d and f are among the easiest. Say each sound aloud yourself and feel where your tongue is placed. Also consider if each sound is long, with air escaping (a fricative) or short, where the airflow is stopped (a stop). Finally think about the use of your voice. Sounds are either voiced (with vocal vibration), or unvoiced.
Learn special IPA symbols for consonant sounds. These include the symbols for sh, th and ng (as in ring). Again make each sound and remember the place and manner of articulation and if the sounds are voiced or unvoiced. Remember it is the sound that is the focus and not the written form.
Focus on vowel sounds. These are often difficult to differentiate as there are 27 possible combinations. The easiest way is to focus on your own speech. Think about the place of articulation and lip position.
Use an online source to practice sound discrimination and transcription of the individual sounds. Once you have fully mastered separate sounds, you can start to combine them and transcribe whole words, sentences and connected speech.
Transcribe short, single syllable words to begin with. Either record your own voice reading a list of words or ask friends and family. This is a useful way to develop your listening skills and identify characteristics from different types of speech. Remember to focus on the phonetic transcription and not the written form. For example the word "cat" is transcribed as /kat/ and the word "mixed" is transcribed as /mIkst/. Progress onto longer, multisyllabic words.
Progress to short sentences once you are proficient at transcription of single words. Again, record sentences and carefully listen to them. A good way to check your skills is to ask friends and family to record unknown sentences for you to transcribe. You can then read back your transcription to them and check for accuracy.
Listen to radio or television programs and transcribe passages of connected speech in conversations or monologues. Remember that in connected speech, one sound will affect another. For example if a nasal sound follows a non-nasal sound both may be said either nasally or non-nasally. Replay conversations and recordings many times to perfect and improve your transcriptions.