Practicing your breathing exercises is a very important part of becoming a better singer. Lying flat on your back, put your hands around your waist with your index fingers pointed toward the center of your stomach. Breathe in until you feel your stomach and hands raise up. Breathe out slowly while counting to 10, expelling air at a steady rate. Repeat this exercise 10 to 15 times in the morning and before bed. This exercise will help you to control your breathing during long phrases where you may otherwise run out of breath.
Practicing your vocal scales at the piano may seem a bit tedious, but it is a very important part of voice training because it teaches you to memorize single notes and the relationships the notes have with each other. Start at middle C, and work your way up or down. Practice singing the same scale in different octaves on the piano, and then begin a new scale. When regular scales become a bit boring, try to work in some chords when you are practicing. This is a great time to work on the types of chords you feel like you are having trouble with, such as 7th or 9th chords. If you regularly sing with a group, gather around the piano and work on singing together. This is a way to understand and master difficult harmonies as well.
Recording and listening to your singing voice as much as possible will help you understand what areas you need to work on most. Purchasing an inexpensive multi-track recorder or even a simple hand-held voice recorder will allow you to quickly and easily record yourself when you practice. Record your scales and see which notes you are having trouble with. Even recording yourself singing along to your favorite songs can help to give you some insight on what you need to work on.
Set a practice schedule. Getting in the habit of doing your exercises and scales is probably the most important part of voice training, because actually doing the exercises is not hard--motivating yourself to do the tasks that can sometimes seem tedious is the hard part. Try to practice 45 minutes to an hour per day if you can. If you truly don't have time to do that, practice for a full hour every other day.