There are several signs of affection, and this answer will assume you are asking this in terms of human affection between men and women. Typical signs of affection include hugging, stroking, soft brushing of skin (i.e. Brushing your hand against someone's arm or face when talking, kissing, holding hands, putting arms around each other. These are just some of the more obvious signs of affection between men and women, and quite often friends, especially girls. Other subtle signs of affection can include prolonged eye contact either when speaking to you or just looking at you (sometimes called gazing), smiling and playing/fiddling with hair is another common sign of affection shown by girls who are shy around guys they like. Girls tend to be more openly affectionate towards other girl friends in contrast to guys with their other male friends; for example, a girl will often hug their friends closely and for a prolonged time, whereas a guy will usually do a firm handshake, or a 'man hug', which is a more manly and firm version, usually involving patting of the back, with less time together. The top halves of their bodies will touch momentarily amidst manly patting, but the bottom half will hardly touch at all as many men find this uncomfortable. On the contrary, girls will often have no problem with full body contact during hugging friends and loved ones, as they are typically more open to affection than many men. This is only a generalised outlook though, and obviously there are exceptions to the rule.
