For your journey to becoming a good singer, a very important skill you have to develop is the ability to identify specific musical notes... or what professionals would call perfect pitch. Most people would say that the skill of having perfect pitch is something only certain individuals are born with, but recent studies and testimonies have proved that theory to be wrong.
Perfect pitch is something you can develop with persistent practice. To acquire this skill, you're going to have to undergo intense ear training. Training your ears to identify different sounds and musical keys is important for speeding up your learning experience. If you can identify a note without resorting to the aid of a musical instrument to find that note, then you've saved a lot of practice time, which you can use to spend practicing on other techniques.
To begin your training for acquiring perfect pitch, you'll need a musical instrument (a piano is highly recommended). Choose and focus on one common note, a C or G perhaps. Play that note constantly while keeping your eyes closed and try to absorb it into your mind. Associate that note with something that could trigger your thoughts, like an experience, color mood, or name. Internalize the note. It's good to also try to relate the note with the starting note of a song you're trying to learn, like C in the Happy Birthday tune.
Don't try to focus on tagging a label for that note if you really can't think of anything to associate it with. What's important is for you to take in the nature and melody of the note. It's highly advisable to continue on with this practice technique even when you're not in an actual practice session. Just keep on thinking of the note, or humming it inside your head as you go about your daily business.
You could also try singing back melodies from songs you've heard of before. Using a portable music device like an mp3, you can play a part of a song, pause it, and sing it aloud to help yourself familiarize the notes you heard. Doing these exercises would not only help you recognize tone and pitch, but could also help you from transposing from one key to another.
Getting an ear training software and installing it into your computer is also a good idea. Try searching the net for that, and get one step closer to becoming a good singer