Well one thing do you know this person? Spells need somewhat of a direct path, if you don't know this person the energy can't exactly effect him [if it could I'd be married to Chris Evans by now lol]
If you do know him, I would talk to him. Meaning, you see him online, say hi and strike up a conversation. You see something he may like, text him about it. While you shouldn't throw yourself at the person, being on their mind will help the spell influence their feelings.
Regarding staying positive, can't really say. With spells I usually just accept it worked and go about my life. Occasionally I'll reflect on the spell [kind of like a confidence boost 'it's cool, I did the spell.'] But for the most part I act normal, maybe focus for the next moon cycle on the specific goal, but not obsessively.
I'm terms of signs it worked, that's more personal so I can't really say specifics. You might get a feeling like someone's talking/thinking of you, an urge to call him, you might also notice him acting differently towards you. Just be observant of your surroundings really.