The only real way to successfully perform is practice. In the weeks leading up to your performance, make sure you make time each day to practice. If you've rehearsed well, you'll do a better job the day of your performance.  Incorporate practice time into your daily routine. Take an hour or so to practice each day. Challenge yourself a little more with each practice session. At first, you may sing while reading the lyrics on the page. As you continue to practice, try to rely more and more on memorization alone. To study your stage presence, try singing in front of a mirror and studying your facial expressions. You can also record yourself singing and play it back to yourself. You can identify any weak spots and focus on those in another practice session. Performing a song is more than just hitting the right notes. You want to know what a song means so you can deliver the lyrics with the right resonance. As you prepare for your performance, strive to learn about the song.  Think about the speaker behind the song. How does the speaker feel and why? With a song from, say, a musical this can be easy. You can look into the character's history. With a song with a more abstract narrator, however, the information you have about the singer is limited to the song. Read through the lyrics and try to analyze what's happening emotionally. How does the narrator feel? Why? Try to learn a bit about the writer of the song. This can help you better understand what the song may be about. If a writer has a sad romantic history, for example, knowing this brings a lot of added context to a love song. If you're nervous about singing on stage, try attending a few karaoke nights with friends or family members. Karaoke can present you with a low stakes chance to test out your skills to a small audience. This can be especially helpful if you're singing a popular song that's likely to be an option for karaoke selection. One of the most important aspects to a live performance is making sure you remember your lyrics. If you're nervous, it's easy to slip up and forget a line or two. There are a lot of tricks you can use to memorize lyrics quickly.  Focus on one verse at a time. Trying to memorize the entire song in one sitting will be too stressful. It can help to walk fast as you recite the lyrics. Reciting the lyrics quickly, with quick body motion, forces you to say them without thinking. This can help the lyrics become an automatic response. Focus in on the lyrics you typically forget. There may be a certain pattern, and being aware of this pattern can help you remember when to focus more during a performance. For example, you may have pronoun issues. You may have a tendency to say "I" and "me" instead of "you." Try to be conscious of this as you proceed to sing for an audience. Feedback can be a great way to prep yourself for a performance. A listening audience can provide you with tips and advice on where to improve.  It can help to choose people who are not afraid to be constructively critical. You want to sing to someone who's willing to give fair feedback. Do not select someone who's overly positive or overly negative. You should also pick someone who knows something about singing. If you have a friend or family member who sings as well, this could be a great person to listen to you perform.

Summary:
Practice. Study the song. Go to a few karaoke nights. Make sure you memorize the lyrics. Rehearse in front of an audience.