Oldfashion, you mentioned that you're 20, that she's 18. I'm really imploring you - don't get too heavy or formal with this. I can almost guarantee that will scare her off. For a first date she needs to have fun, you need to have fun. I'd say just have your place clean, I really wouldn't have much in the way of music playing at all unless its really not that noticeable, maybe some TV, but keep the atmosphere as non-tense as possible. I wouldn't light candles (unless they're off the dinner table and because you like them in general), I wouldn't try to influence the mood with colors, the only way I would recommend is making her feel comfortable at your place and like she's hanging out with a cool and fun guy rather than scary. The two of you should BS about life, work, how she's doing, what's going on the upcomming weekend, etc.. That said as well make something for dinner that's more hip and trendy rather than heavy or romantic, ie. I don't know that I'd bring out shrimp alfredo and pinot grigio unless that's what you're in the mood for. If you want to you could even envite her over to cook with you - that could be neat. Overall the most important thing is that she thinks your cool and has fun, if its even just slightly - subliminally - romantic that will be plenty, anything too forward on a first date would probably seem a little off or creepy.
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