As I'm writing this, I'm thinking over my life, and I do recall this happening to me many years ago. When I realized it, I was to scared to do anything about it. Instead, I did the typical thing of telling God to work everything out. Not realizing it was God who allowed the love I had for "this person" to take root in my heart in the first place. How could I not see that our all knowing God already knew this was happening anyways. Now God had been waiting on me. This was another great lesson in love for me that I missed, and I don't intend to repeat again.
People often times think that love springs from their head; therefore, love must logically occur. Love springs from the heart. This is the place where your love for Christ is found. Think about it for a minute. Because Jesus lives in your heart, it makes it possible to have compassion where compassion does not exist. It allows mercy to be found when mercy has vanished. This love also extends grace when grace is not deserved. In Proverbs 4:23, we are to guard our heart not to keep love out, but to make sure what is flowing from our heart reflects the love of Christ. So when a person discovers they are in the center of God's will for their life, this can and does include loving someone you never thought you would.
If love has arrived quietly and unassumingly toward a particular person, you need to acknowledge it to God, be a participant in the process, and give Him permission to direct the fulfillment of this love. This does not mean you sit back and do nothing. You must be available for the opportunities that God presents concerning "this person." Maybe just maybe God allowed this love to arrive quietly, because He knows you, He created you, and He knew in advance that you would want to control every finite detail or possibly rationalize it away. So, no, there is no set way in how love arrives. Whether it is bold, cloudy, or quietly, when love arrives, put your hand on the door knob, open the door, and let love in!