I have recently taken up singing backing vocals and occasionally singing lead and i'm really enjoying it now. I found that previously the only times I would sing would be to myself and they would be very quiet. Now that I'm singing properly I find that singing with confidence really makes a 100% of the difference. Having the confidence to project your voice singing loud and clear will result in better vocals. If you go half arsed at it your vocals won't be anywhere near as good, or in pitch. It really takes just having the confidence to push out your voice to make the difference.
I really believe that everyone can sing and in pitch, its just a difference of how confidently one goes about it. Singing lessons will help anyone a great deal. Learning how to project your voice, using proper breathing technique, warm ups and how to place your voice. Most people will tend to singing from their throat, whereas if you using vocal placing techniques you can sing from the front of your mouth and you can save your voice from being sore after singing for extended periods.