Even if you're attracted to someone in a big way, now is not the time to pursue anything. Your attractions just aren't trustworthy now; you might be responding to mere physical beauty but turning it in your mind into something more, fantasizing that you could build a real, long-lasting relationship with someone just because they're good-looking. And the paradox of this is that if you were to start getting to know that hottie now, the attraction would probably fade so fast you'd wonder if it was ever real in the first place.
If you've got the hots for someone but then find, as you get to know them, that their personality is lacking, the way that you see them can change, fast. You'll wonder what you ever saw in them. Another possibility for this transit is that your attraction to this person's looks won't fade, but you'll start feeling vulnerable and insecure as soon as you start getting to know them, and you'll grow jealous and possessive, clinging to them to try to hold on to something that you never had in the first place. Get to know someone slowly now, maybe via emails, before you try to turn a flirtation into something it's not.