A radiant love for Christ.
A love for God's Word.
A spirit given over to God on all matters.
Unique, and thoughtful, responses to common questions.
A genuine smile.
Simple style and belongings...nothing too trendy or too excessive.
A good book that they may be reading.
A particular involvement sometimes...like missions, or soup kitchens, shelters, etc.
Music, art, and theater...the love of any of these always catches my attention.
A baseball fan...especially if it's the Cardinals. :D
Oh, I am sure there are more, but these are a few things that make me notice someone.