If your question is how do you tell someone you like them physically, and by that you mean in a sexual way, I'm not exactly sure there is a correct etiquette for that, however you could try being honest and up-front, most people prefer that approach.
If you are asking how to physically tell someone you like them I think a hug is a good start, however manners dictates that you should approach them from the front (sneaking up on someone and hugging them unexpectedly is a fast way to get an elbow in the solar plexus ) and make some sort of declaration of intent before wrapping your arms around them.
you tell someone you like them by your body language.
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Tell someone that you like Emily for example. Then tell the someone why you like Emily, and get out so it's not bottled up inside you. This worked for me when I was afraid to tell the person I liked them.
tell your feelings to her/his friend and let her/him tell to the one you like!
how you tell someone you like them is just to be your self around them and ask and see if you can tell them something and Say it
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if they are rude to you
you ask them out.
No you can not
Just tell him that you like him better as a friend.
Bang em and see if they like it
Write to him, Simple!!