Learn music correctly from the start! If there is a difficult passage, practice it very slowly to ensure that the pitches, rhythms and words are correct. If you start more quickly than you’re able to, you will learn things incorrectly and have to work twice as hard to unlearn and relearn the correct way.
Use a metronome to train your tempo sense keep a steady pulse. Many singers have problems because they do not pay attention to tempo.
Break difficult passages down – just pitches or just rhythm. Pay attention to articulations and dynamics, learning them from the beginning.
Make sure all parts of your solo are prepared – don’t always start practicing at the beginning of the piece. Work intensely on different parts that are harder, and don’t over sing easy parts. It’s better to sing a new, different piece than practice only the easy parts of something you know.
Practice “backwards” – sing the end first, then back up one line or verse, until you reach the beginning. This will enable you to feel more confident, the further you get into the piece. Use the same method to master longer, difficult passages (e.g. sing the last 4 notes or words, then the last 5, then the last 6, etc.).
Record yourself! Any type of recorder works, even a phone. This will help you identify elements that need improvement (notes, rhythm, intonation, diction). This is one of the best learning tools.
Once you know the piece well enough to go through beginning to end, practice singing without stopping, even if you make mistakes. It will help you get used to letting go of mistakes that may happen and keep from compounding them as you continue. Of course, remember where you have problems and focus on fixing them in subsequent practice sessions.