Solution: Keep the microphone's screen 0 to 3 inches from your mouth while singing and "aim" it at your mouth. Equally important is to not sing to the microphone, but to sing to just beyond the end of the microphone. Vocal projection is very important for establishing a strong vocal presence and will ensure your message is delivered to your audience.
Problem: Many singers have poor mic technique. Some singers don't understand proper mic technique, so they don't know that they're doing anything wrong (after all, ignorance is bliss!). There are many available resources online that will teach you good mic technique. Simply reading the owner's manual of the microphone will put you one step closer to proper mic technique. I pasted a basic example of a Google result for "proper mic technique" below. There are many more instructional videos on YouTube, etc.
Background: Many times people will (not so nicely) complain to the sound engineer that they can't hear the singer/speaker. Many times we get blamed for it. More times than not, this is user error on the performers end, not the sound engineer. If you're holding the microphone at your waist, no amount of volume will help the listeners hear you. Vocal microphones are built with a specific volume threshold for optimum performance, similar to your car or your lawn mower requiring certain gas for great results. Putting water in the gas tank is not going to end well; why would ignoring the microphone's user manual work any differently?
Mitigation: Watch your favorite performer sing into their microphone and take notes. Video tape yourself singing – you might be surprised that you hold the mic farther away from your mouth than you think, or that you don't always "aim" it your mouth. Practice with a mic at home or the rehearsal space to hear the difference in a controlled environment.
Your great mic technique will help your listeners hear you, and will help ensure great sound out front.
Google Result (taken from http://www.ehow.com)
If you have the option, choose a microphone you feel comfortable handling and you feel complements the qualities of your voice. Experiment with different types of vocal microphones (you can call us about this to hear different mics and get a list of others that we don't have in our inventory) to see how each one sounds different and reacts to your voice. Try to use the same sound system in the same space when experimenting with microphones to element all other variables.
If you can, work with a competent live sound engineer (can I recommend one for you??) you trust and are comfortable with to practice your microphone technique. He or she can give you advice and pointers on how to make the microphone perform its best and help you understand how your particular microphone works.
Point the top of the microphone directly at the front of your mouth, holding it one or two inches away and just under the lips. Don't touch the microphone "windscreen" with your lips, or hold the microphone to one side of your mouth. If the microphone is on a stand, adjust so that the microphone is correctly positioned as described.
When "belting out" louder passages, move the microphone away from your mouth slightly. For quieter passages move the microphone closer in. This isn't to control volume but to avoid overdriving the microphone element for loud passages or producing a "thin" sound for quieter parts. Of course, if the microphone is on a stand, your head will have to do the moving and not the microphone!
Practice and experiment.