Imam Suhaib Webb talks about the close relationship with Allah that one can gain through making du'a. He discusses it's importance and it's power.
What I learnt is that Dua is the essence of worship, sign of someone's sincere tauhid to Allah SWT. Allah is Al A'lim (the ONE who Knows) and As-Samiq (the ONE who Hears) and its better for us to recite our dua in a hushed tone. The beauty of dua is that Allah will listen to anyone who calls to Allah via his/her dua since He even listens to the dua of the Iblis. And there is no dua in the quran that starts with "Ya"...because its a sign that Allah is closer to you than you think so call upon Allah with your dua and Allah will answer you, insya Allah.