Listen to the piece several times before attempting to transcribe it. It is very difficult to transcribe music that you are not familiar with. Listen to the piece at least ten times before attempting a transcription. Start with the melody in the first couple of measures. If you can nail down the melody, then the chords will be easier since the melody will help guide you and make it possible to place the chords in the right place. The key to a successful transcription is to use your listening skills. If you are not familiar with the piece, you must become familiar with it through repeated listening.
Set the music on a loop where you only listen to 2 to 3 seconds at a time. Work on these increments of sound until you have that section notated perfectly. Frequently play back what you have notated and compare it to the original song. If it sounds correct, move on to the next 2-to-3-second segment of the piece. You should be checking each chord on a piano, or, if you do not have access to a piano, a music notation program.
If you are having trouble notating the melody, then try just notating the rhythm. Start with the melody's rhythm and then begin to transcribe the rhythm of the background parts. When you have a rhythm notated, double check it by tapping the rhythm along with the recording. It may be necessary to do this several times before you get it right.
There are some programs that can help to make transcribing easier. While it is better to work in real time to develop your skills further, a software program can help you complete a transcription much faster initially. These programs can slow down an audio recording, pause and loop sections of sound making it easier to transcribe a piece. Digital Transcriber from NCH software has a free program that will help you with your transcriptions.
Transcription is a difficult process and there are no shortcuts that can be taken, so the best trick of all is just putting in the time it takes to become good at it. A program that slows down music can make the task easier, but if you truly want to improve and become a better transcriber, you must put in the effort required to transcribe music playing in real time. The benefits to learning to transcribe music on your own include a more fully developed ear and increased awareness of music.