Most Helpful Guy
You don't it can't be subtle guys don't get or see subtle. if your going to do it then you have to let him know that you like him. Suggest that you would like to go on a date with him sometime. Don't ask him out if you don't want to but suggest it.
I hope it works out for you. It did with me and my girlfreind. Though she had terrible timing things worked out. :)
Most Helpful Girl
Pay attention to if he gives you special treatment over other girls. Try flirtatious glances where you smile with your eyes and grin at him. Guys can't resist that look. If he tries to separate you from other friends so you can be one on one also a good sign. If he copies/ mirrors you.. Also really good