Well, I definitely think that that is one of the great techniques to use. At first, when starting out with cold approaches, your more worried about getting over the fear of approaching itself than about what you say. So having a default opener is a smart idea for sure. Personally, I would suggest taking it step by step. The first 10 approaches, come up with an opener that will allow you to stop them and then whatever, but it shouldn't lead to an actual conversation(unless it does), and should just be there to get over the fear itself.
For example: I suggest a couple things. Maybe a humorous comment or question, if this doesn't get her laughing, atleast you'll be laughing... on the inside. What I personally did for my first 10 approaches was pretty simple...
If a girl was walking, I'd "stop" her and ask her "Can I ask you a quick question?" Sometime she'd say no, but most times they'll say yes pretty reluctantly... Then simply ask "What's your name?" or what I did just for laughs was ask "Who are you?" in a very questionable tone. I got a lot of rolling eyes but hey, after the 10th time I felt like I could say anything and was ready to move on. Basically, you can insert whatever you want here but just use it to get over the initial fear. Could I have picked a better opener, sure, but I was just saying something and if the response was negative(which was usually the case), I simply told them that it was a pleasure meeting them with a big smile and walked away. Emotionally, it makes you feel like your in control.
After this you should work on an approach that will actually lead to some kind of convo. A little trick that I use is to stop a girl and ask her "Hey, for some reason you look kinda familiar... Do I know you from somewhere?" They usually say no which is when you ask "Well what school did/do you go to?" If they say a school you went or go to, then continue from there but if they say another school... use this to your advantage. Don't simply say "Oh ok, nevermind"... Ask them how they like it, hell start talking about why you think your school's better and so on a funny way. You can substitute work, city, or whatever in place of school but the point is, you are getting her talking about something, even if it is kind of a sneaky way of doing it.
Alright, well this is the part where your going to have to be creative. Once you feel comfortable saying anything to random women in cold approaches, you need to move on to the situational opener. This is where you gotta improv and say something to to the lady in correspondence with the surrounding. Ask her or comment on something she's wearing, something that's going on around you, something you see, what the time is, the location of something. And then follow that up with something else and get the convo rolling. Here's an example...
Say your on campus and your looking for a building on the first day of class, or hell, even the middle of quarter... or maybe you're not actually looking for a building at all. Well you see a woman walking towards you so you ask her if she knows where the building is... "Excuse me, do you know where building 15 is?" Her: "Umm... Yeah, it's [wherever it is]" At this point you can say any number of things...
"Yeah I felt kind of embarassed asking you, but you looked like you knew your way around this place"... Or even take out the first part of that
"Yeah this is my first day here/I haven't been going here very long/I don't usually have classes in that area/I have to drop something off for one of my classes (basically whatever)... And then ask her a question in relation to what you just said... "So how long have you been going here?... Do you have a class in that building?" and so on.
Well that's just one example but you get the point.
After this work on building rapport and getting numbers and stuff, most of this stuff is covered in the DJ Bible anyways.
And then at this point you should be getting the gist of what to do. Here are some tips for cold approaches...
1.HAVE FUN! You think getting rejected sucks?... Make getting rejected a thrill that you ENJOY.
2.Most people think of two outcomes in a cold approach, succeeding or not succeeding... Well, in my opinion, if you think like this you will ALWAYS FAIL! Sure, you might not always get a number, but in my opinion, a rejection is a success just like anything else. Therefore, if you cold approach, it is a WIN WIN situation. If you get rejected, you walk away feeling kind of embarrased at first, but crush that feeling RIGHT AWAY. Then you will feel proud of what you've done, and the next day, believe, NO ONE will be laughing at you. And on the other side, if you do get a number... HELL YEAH!
Well, I'm done writing this novel, congratulations if you read it all.