It's impossible to love someone without knowing the other person first. When you meet a person and you feel strange, you don't love the person, you are only physically attracted to the person. It's possible to really love the person after knowing him or her.
Physical attraction is important. Some people look good in the outside but when you get to know them, they are hallow inside, they don't have the right values. There are others who are not physically attractive but have a heart of gold.
Love at first sight is actually not true, you have to take time to know the person. Good luck.