I guess it`s a problem for most of us

What I do (and I`m not a singer, by any means) is to wait while there`s nobody at home, get over feeling stupid for not hitting the notes and then fool around with it. Try singing a random note and then find it on the fretboard and then work your way from this

I`ve heard that it`s easier to sing in the keys of A and B, since they`re not too high or too low.
Also, I really like the feeling of finding the note, it feels exactly like when you tune your bass - first, it`s a dissonance, then you`re getting close and your voice starts vibrating and then - it`s unison.
Regards,
Clayman.