You love them and you want to let them know but you want to do it in such a way that you do not scare them off. Essentially your problem is how to subtly let them know that you really like them (much more than a friend) without coming on too strongly and overwhelming them so that they bolt. You want to use various understated and under the radar ways to slowly draw them to your side. And your question is; how to do this without scaring them off?
1. Attentively and considerately! To show someone that you care about them you need to be attentive to them and to take into account their feelings, concerns and interests. Nothing shows your interest in a person than listening to them and actually hearing them. To hear them when they talk you need to pay attention and really listen to their words and watch their body language and then let them know that they are interesting to you by asking relevant questions and making appropriate comments. And think about their feelings, concerns and interests even as you are attentive to them. Treat them cordially and ensure that you do not hurt their feelings by saying or doing inappropriate things. And if you tell them that you will do something for them or you will be with them at a specific time then you need to do as you said and do not inconvenience them.
2. With warmth and friendliness. To show someone that you love them you need to treat them with warmth and to be their friend. Being indifferent, cool and aloof may work for your non romantic interests but if you really like them and want them to know then you need to thaw out. As a friend you will have fun with them; you will talk about everyday and serious things with them; you will tell them your secrets and you will keep their secrets; and you will stand up for them when others criticize them and you will stand with them during tough times. You will thus be affectionately engaged in their life as a true friend.
3. Intentionally! All these things you will do on purpose. So you need to determine in your heart that you will do these things even when you would rather focus on yourself. The person you like and are behaving like this to will slowly begin to reciprocate but you must be the initiator and the one who carries the relationship until the person you like reciprocates all that you feel. To show someone your love requires your inner motivation and purpose that this is something you want and are willing to invest in otherwise you will run out of energy and patience.
4. With your ability and practically. To show your love you must do things for the object of your affection. You know the saying 'words are cheap' well it is true and you just cannot speak yourself into a relationship without doing any deeds of love. You will need to use your resources which will include your money, your time and your gifts to do imaginative and memorable things or deeds for the one you love. Only your imagination and your resources can limit what you can do.
To show someone your love requires that you implement all of these 4 components. As your love becomes clear and obvious to them they will in turn reciprocate but make sure that at the appropriate time you let them know that yours is a romantic interest and not just friendship. There is nothing more frustrating than being treated only as a friend by someone you love and want more from.