It's very important to always warm up our voice before we start our practice. It's a simple exrecise to increase the flexibility of our voice and to also warm up the vocal chords before we start singing more complex things.
Practice singing the 7 notes which are S R G M P D and N for as long as your breath lasts. Do this in a pitch that is comfortable to you. So, start off by taking a deep breath and then sing each note for as long as you can.
The next exercise can be singing the notes as aakar, uukar, mmkar and omkar. This is very good for our voice - helps opening up our vocal chords. Singing the akaarms in slow and then fast speed can be tried out.
Hope you enjoy doing these :)