Warm ups need to cover the following elements:
Posture
Breath control
Intonation
Voice Placement
Tone
Projection
Flexibility
Range
Musicality
See this document HERE to see which of the following voice exercise examples would cover the above elements (You should already have a copy of this).
Audio examples of exercises
arpeggio with long high note at end (crescendo)
arpeggio up and down with long high note in middle
ee/ah/eh/aw/oo vowels on a pitch
Long notes (any vowels) crescendo/diminuendo (messa di voce)