Find a space you can be alone and feel uninhibited when you are practicing. If you play any instruments, put them in your space along with your chair, your CD player and CDs, radio, MP3 player and/or iPod and dock.
Each time you practice, take a glass of water to your space. Drink a little as you go to stay hydrated and energized.
Stretch your body before each work session. Singing is a physical activity, and strain in the body causes strain in the voice. Roll your shoulders back; stretch your arms, legs, and back; and allow yourself to feel loose.
Practice breathing correctly. Push your gut out as you breathe in, like you're filling up a balloon inside your body, and push your gut in as you breathe out. Do this at least four times per practice session, and try to incorporate it once you begin singing.
Warm up your voice. Start by gently humming at a comfortable pitch--one that is not too high, not too low, and comes out with very little effort. To hum, gently put your lips together (almost like a kiss) and, with your mouth closed, try to make space in your mouth by raising your soft palate. (Basically, imagine you are holding a hard boiled egg in your closed mouth.) Make an "Mmmm" sound and try to send the sound forward through your nose. It may tingle a little, but that's good. Move the pitch up and down as you hum.
Push your lips forward and try to get the clearest sounding "Eeee" sound you can get. Try to send the sound out through your nose and forehead (use your imagination) and practice proper breathing as you do. Make the "Eeee" move from high to middle to low and back up again. Vary it as you go, by visualizing that your voice is actually running on a real roller coaster track.
Play a song that you like, know well, and have readily available. Sing along, but don't use any words; instead, use that forward "Eeee" sound you perfected a moment ago. Try hard to listen and match pitch with the singer, but don't try to imitate his or her voice. You want to be a better singer, not a cheesy sound-a-like.
Go back through the song on the "Eeee" sound again, focusing on spots you had trouble with. Take those parts out and work on only them, alternating between the "Eeee" sound and the actual words. If you feel confident about your fixed spots, sing the whole song through again, this time using the words.
Try a song that is harder for you, perhaps one with some higher notes. Repeat steps 7 and 8.
Think "down" instead of up when attempting high notes. Most times, when people go for high notes, they "reach" for them. The chin goes out and up, head goes back, neck extends, and tension fills the body. This makes matters worse. Instead, think down. When a high note comes along, squat to pop the high note right out of you. Another choice is to use your chair. Put one leg up and lean into the leg on each high note.
Try another song that is harder for you, perhaps one with some lower notes. Repeat Steps 7 and 8.
Imagine that your mouth, throat, and body are parts of a cave for the harder-to -reach low notes. Your voice is ringing through this cave. Near the front, it is high pitched, light and bright, but as you go down lower, the tone is darker and meatier. Imagine your voice simply dropping into the lower ranges of the cave.
Practice for at least a half hour. By the end, your water should be gone.