How Can I show guys I'm interested?

You already are. Consistency helps. But he might be so damn shy as not to notice. He could be clueless like me and not notice when women do those things. Keep at him.You'll either scare the daylights out of him, or one day he'll have this red mark on his forehead where he hit himself with the heel of his hand.

you can walk the opposite way of him and when you can near throw a smile and *wave* at him. if he waves back that's your chance to talk. if not keep persistence until you get a no, the dude is shy and has no balls lol.

He might keep looking down because he is actually interested and just like you is shy and unsure of what to do. Eventually one of you will have to make the first move. I know how you feel, I'm from the outback and shy as hell but you just have to swallow your fear and give it a try. Start small with a conversation and just get to know each other a bit and go from there.
If you really want to keep his gaze you could just flash him. lol, just jokes. But seriously a lot of guys take interest in girls but can't act on it. so ull just have to take a chance.

Here, it is this simple.Go up to him next time you two are in each others paths and say "Hi, I'm Majorie." .I'm guessing that's your name? That's to start it off. I was pretty shy until I bit the bullet and just said "Hi" and introduced myself and had a conversation about basically nothing, just fun small talk. Give it a try and let me know what his response is.

Whats up with that guy? He sounds really shy, or just. weird. :p
Do you need advice on how to get HIS attention? Or just guys in general?
Well not every guy is like that cute guy you work with. Most of them will say thank you if you open the door for him, but then, most guys would be the one opening the door for you.?
But anyway, to get guys to approach you, you will have to look comfortable, and friendly.
Since you are a shy person, you probably come off as snobby. You probably don't realize it but you probably make guys nervous.
Anywayz, when you are out, try to smile alot. Not to yourself, because then people will think you are weird. If your eyes meet with someone, then smile at them, and then look down, or look away. Its a shy way of flirting. Or when you are with friends, smile alot. It will make you look friendly, and approachable.
Shy people tend to avoid other people. Like, they either sit in the corner, or at one spot. or talk to only certain people. Try to mingle. If you are at a party, try to walk around, and mingle with people. ALot of guys are shy too, and they get really nervous about talking to a girl. But if you show that you are open, and easy to talk to, then they will feel more comfortable about approaching you. Just don't talk too loud, or laugh too loud. Because some guys can tell when a girl is desperate for attention. Just be yourself, smile, and make eye contact. Show you are interested by listening and paying attention. :)

You have to reach out to him otherwise, he has no way of knowing. You can pinch him or tickle his sides a little when you say hello. Or touch his arm. Get into his personal space and see what he does. If he doesn't back off, he is interested too.

Good luck!