Play along with acoutic guitar or piano/keyboard. Not electric guitar. (this comes later when your voice is trained)
Smoking is a big no-no. Certain foods are a no-no. (before practice, such as greasy food, and startchy stuff)
Warm tea is a yes-yes for warming your vocals up.
Singing a "style" that suits your voice is a yes-yes.
Singing along to a scale UP and down Is a YES.
And there are numerous Methods of warm ups you can use.
Here is me on youtube;
http://www.youtube.com/watch?v=0cBFU5nqYLgNot actually sung at my best, i prefer it to be on cappo on third or second for this one.