Like I said: you seem like you’re a really interesting person and I’d love to get to know you. Hope to talk to you soon, YOUR_NAME”
Give it a somewhat offbeat subject line in order to stand out from the crowd – I’ve always had success with “Pirates are inherently cooler than ninjas” – and send it on its way. It takes slightly longer than hitting “wink” (unless you’re like me and kept two to three variations in a text file that you could copy and paste in as needed…) but it’s also far more likely to get an actual response instead of a silent eye-roll.
This is possibly the biggest time-waster when it comes to online dating: taking too long to actually ask her out on a date.
Look, I get it. If you’re not the most assertive or confident person, you may not feel comfortable asking somebody out on a date early on. You 
may be trying to feel things out and get to know them. You may be trying to avoid getting shot down and want to wait until you’re absolutely sure that they’re into you. You may be worried about coming across too strong or looking too interested; after all, the person who’s less invested is in the dominant position, right? Right?
Here’s the problem with that attitude: the longer you wait to actually ask her out, the more likely it is that you’re never actually going to meet her in public. By spending so much time trading emails back and forth, you’re bleeding emotional momentum. That initial rush of interest goes away quickly if you wait too long to actually make your move; they’ll almost always start to assume you’re not that interested in them after all.
Moreover: you’re almost certainly not the only person she’s talking to. If you think she’s attractive, then other people do too… and the longer you take to actually say “hey, I’d love to get a drink with you” or “I’ve had a crazy idea: would you like to go to a sushi-making class?” the more likely someone else will.
What Should You Do Instead
If you’ve been exchanging emails back and forth, then they’re interested in talking to you; take “yes” for an answer and say “You know, I think getting to know someone over drinks is better than just emailing back and forth, don’t you?”
How do you know when to ask? It’s fairly simple: the magic number is typically when you’ve exchanged 3 or 4 emails. Watch for the length of the reply. Much like talking in person, if they’re writing long emails or asking lots of questions, they’re definitely into you; short, terse responses mean that they’re not quite feeling it.
The best thing about it, though, is that it’s a no-lose situation. If you ask and she says “yes”, then congratulations! Go out and ace that first date. If she says “not yet,” but suggests maybe another time soon? She’s still interested but needs a little more time to be comfortable. She says no? Cool, you don’t need to waste any more time with her; move on and find someone who does want to go out with you.
You’re Talking To Only One Person At A Time
Online dating isn’t like meeting people in real life. Narrowing your focus to only talking to one person – especially if you haven’t even gone on your first date with them – is a mistake.
Even if you’re a confirmed serial monogamist, narrowing your focus to only one person at a time is a mistake. You’re putting all of your metaphorical eggs in one basket and – this is key – making the unwarranted assumption that they’re doing the same. Like I said earlier: if you’re interested in them, odds are that somebody else is too… and your online honey-bunny is talking to them, too. Odds are good that they may well be going on dates, as well; not everybody is going to put all other interactions on hold just because they’re talking with one person or another.