If you're looking for some techniques to improve singing voice, the you are on the right site. As you go along on practicing your voice lesson, you must remember that you have to avoid straining your voice.
Always warm up before you start singing your songs. I recommend some relaxing breathing exercises then gentle humming first. Don't sing too loudly at first. Give your muscles time to prepare. If you feel that something is too high then sing it an octave lower. You will need to have a set of exercises that develop different aspects of your voice and musicality they should include major, minor and chromatic scales and arpeggios in a variety of pitches using different vowel and consonant sounds.