Often during prayer, we take the initiative and present all of our needs and wants before God, pouring out our heart to him.
During contemplative prayer it is typically the opposite. We wait and listen to God and his hidden voice.
The Catechism of the Catholic Church explains this aspect of contemplative prayer:
Contemplative prayer is hearing the Word of God. Far from being passive, such attentiveness is the obedience of faith, the unconditional acceptance of a servant, and the loving commitment of a child.
Listening can be difficult for us, as we tend to always want to do something during prayer.
The key is to listen as the Blessed Mother listened to God:
[Contemplative prayer] participates in the "Yes" of the Son become servant and the Fiat of God's lowly handmaid.
This listening forces us to slow down and open the door for God to enter in.
Contemplative prayer is not a type of prayer to casually choose to try out, but should involve a conscience effort to pause and listen to God's voice.