Alright, let me get this straight. Let's say you go to a friends birthday, and you meet a girl. She's funny, you like her, you and her share a lot of common interests, whatever and so on. Why does it matter if she's tried weed once, or enjoys a little drink on the side, or has the odd cigerette? Here's a hint: it doesn't.
If you 'click' with her, then that's all that matters. Cutting out girls who drink, girls who smoke, girls who've done drugs (whether casually, or just that one time to try it out) AND girls who have had pervious sexual partners is going to seriously limit your potential "pool" of girls. And, into the bargin, this pool is only going to get smaller and smaller as you get older; girls will just naturally have more sexual partners the older they get, on average. Drinking alcohol becomes less of a taboo when you hit 18/21. Most people don't find illegal drugs all that reprehensible.
Hell, I've tried illegal drugs once. Just to see what it was like. It wasn't for me, but hey, I moved on. I do, however, drink on a semi-regular basis. If a girl were to reject me based on either or both of those facts alone, rather than, say, my personality, or the even how I look or whether she's attracted to me or not, I would think she's not only a bit of an idiot, I'd also think she's incredibly pretensious and stuck up.
It's cool to have morals, and if you don't want to drink, smoke, do drugs or have sexual partners before a certain milestone (be that age, marriage or whatever else) then good for you; that is entirely, 100% your call. You can NOT expect other people - who may not even know you yet - to maintain the same standards. It is, however, reasonable for you to explain your morals and principles to a girl, and it is also reasonable for you toexpect her to respect your morals and values.
But you get what I mean. 
