It pretty much goes without saying that practicing is essential to mastery of any endeavor. Anyone who is serious about his singing recognizes this fact. It goes with the territory. What I see as a problem is that students often just don't know HOW to practice efficiently. They blindly jump in without a game plan that will allow them to optimize their practice room time. Well, not to worry- that's why I'm writing this little entry. Here are some helpful guidelines to make your hard work more effective.
1) Set goals for the practice session. Go in knowing what you will be working on. What songs will you tackle? Will you be rehearsing songs you've already learned well? Are you just running problem areas? You can always tweak your plan as the session goes on, but have a plan to start with.
2) You should ALWAYS start your practice time with warming up. Do some physical stretches as well as tongue stretches before launching into your vocal exercises. Humming, lip trills, and 'ng' sounds should start out the workout.
3) If learning new songs, you need to break them down and learn them incrementally. Don't start out trying to sing the tune full blast with words. This can be taxing to the instrument. Begin by vocalizing the melody on a lip or tongue trill, hum, exercise syllables (goog, mum, wun, nay), or a single vowel (I like 'oo') so that the vocal muscles can get used to creating the pitches accurately. Learn the lyrics independently of making pitch. Let the articulators get used to making all your word sounds efficiently. Only then should you start singing on the text.
4) If you are working on numbers that you have already learned but have problems, take the trouble passages and phonate them on exercise sounds to get your vocal coordination back on track. Then add the words back in.
5) Record yourself often as you practice. The immediate feedback you get from hearing yourself goes a long way in fixing problem spots in your songs and in your technique.
6) Practice in front of a mirror. This goes for technical exercises as well as songs. Watch for undue facial tensions, bad vowel shapes, and high, shallow breathing.
7) If you've had a long or very intense session, wrap up with a vocal cooldown. You will essentially do a shortened version of your warmup in reverse. It's important to bring the vocal folds back to their normal speech state.
These tips will help you to make your practice sessions more productive and, in the process, allow you to be a better artist.