Imagine you are a teenager at the mall. You see that person of the opposite sex that you're attracted to. Smiling, Flirting, and eventually a phone number is exchanged.
The first time that person calls you, your immediate response usually is "Who Is This?" because you don't recognize their voice...
As time progresses and you spend time together- in person, over the phone, writing notes, texting,etc. you get to know one another's "voice" - it is not just an audible sound but the style in which they speak, write and respond.
Right now, my husband could call me from a payphone on the side of the road, and I'd immediately say "where are you calling from" because it is not the caller ID that makes know that it's my husband on the other end of the phone. It is because I know His voice.
Spending time with God will enable you to "hear" His voice. When you get that "gut feeling" or "intuition" you will know when it is God prompting you. When you read something that pops out at you and you cannot forget about, you'll identify when that is God responding and directing you. Spend time together and you will get to know God's voice so when he speaks from an unusual place, you'll know it's Him, because you KNOW Him.