I am ugly, but my brother is attractive. IMHO here are the signs to establish wheter you are ugly or attractive (based on my experience)
Signs that you are attractive:
1)People approach you a lot. Girls touch you when talking (this does NOT apply to very tactile persons who touch almost everyone) and have a flirty vibe toward you. When talking, they want to keep the conversation going. People seat next to you if they can, and invite you to social gatherings. If you approach other people, they are happy and smile at you (especially girls).
2)If you are the one who makes eye contact with someone, he/she says "hello" or smiles.
3)You receive compliments from people you meet the first time. Some of the most common are "you are handsome", "your eyes are beautiful". But there is also stuff like "you have a kind face", "you dress well", "you seem a good guy".
4)People often ask you if you have a GF or just assume you have one.
5)Not necessarily a sign...but it's possible that you grow *very* extrovert, confident, friendly.
Signs that you are unattractive:
1)In social settings, you are usually left alone. People don't talk to you, except for random reasons or when you go talk to them. And if you approach them and try to create a longer interaction, they don't keep the conversation going. People somehow view you as "a weird one" for not interacting and as even weirder when you try to interact.
2)If you are the one who makes eye contact with someone, he/she notes you, but does not react with a greeting or a smile.
3)People don't say that you are attractive ( your relatives do NOT count as they are used to your face, of course your mom thinks that you are handsome, so does mine lol). You hate yourself in most pictures (not matter the angle, lightning, pose etc) and consider yourself ugly (unless it's really a BD, it's possible you are right). Not very likely to happen, but...mean people or people who want to insult you when you get into heated arguments, may say "you are ugly"; it's one of the first insults coming to their mind.
4)You are never asked if you have a girlfriend. It's often assumed you don't have one. You probably don't have one.
5)Again, not necessarily a sign, but it's possible you will develop a *very* shy, introvert, and wallflower personality.