Here are some of RaMed Studios suggestions to help you get your vocals right. Some days you can sing all night without a problem. Other days, you might wear out by the second or third song. You may even have noticed that some days you can hit that high note, but other days its a stretch to come near it. You may find that you're able to sing lower notes in your range at the end of the day than you can sing in the morning.
RaMed Studios suggests working out ahead of time by warming up your voice prior to a recording session or performance. Record yourself at home and listen back to get an idea of what needs improvement. By doing this daily you begin to develop your vocal strength and bring your vocals to tip top shape where you can now show versatility as a great singer.