If the young man you saw in a public place, your task – to push it to the acquaintance. This can be done through a radiant smile, addressed to him personally, and more complex methods. For example – if you're both riding the bus, sit, get a crossword puzzle and after a while ask him a word. Or ask to open for you a bottle of water, or to help make something equally simple. After he will help you, and say thank unobtrusive compliment. Then have him do it.
In a situation when you and your boyfriend already know and are waiting for his action, be more attentive than to the other guym: often smile, enthusiastically listen to what he says, laugh at his jokes. Casually touch. Your touch will make him notice you, if he's still not done. But don't be Intrusive. Your case is a little push, not to drive it into the corner of the manifestation of your sympathy.
Send him a text about some celebration. Better if it is not quite a formal occasion, like a birthday or New year. At this time he will get a lot of messages. Ideal birthday or a professional holiday. Try to make your text was personal and memorable. Do not download the text of the message from the Internet, write for yourself.
Ask for his help to pump up the bike to fix the computer. At a time when he could help, say, how well it all turns out. The next day also thank him and tell him how much he helped you. If he offers his help in the future, use it in the near future. Just be careful that the aid was quite easy and no it is not strained. Exploits – it's all in the future, at this stage it is important not to scare the guy.
A good method is to ask him for advice. It includes all the advantages of the previous version and does not have its disadvantages. The young man does not have to strain by giving you advice. At the same time he will feel that in your eyes he is an important and authoritative person that will give courage to the most timid guy.