However, beginners may practice too much and should stop if they feel vocal tension. Taking breaks during the day allows those who don't have vocal resistance to practice more daily. Singing students usually practice two hours or more every day. That doesn't include time spent learning to sing, dictate, play the piano and absorb knowledge related to singing, such as anatomy, music theory, and the history of music.
Basically, any place where you can sing is a good place to practice, but make sure you don't strain your voice by singing crushed under the kitchen table.