No, you should also tweak it while you are calling. The funny thing is you'll know instinctively when something is not working. Doing it right away keeps you from forgetting what your "little voice inside" is telling you. You should also note what is working for you, in case you forget at a later time.

In the evening you can take time to evaluate your whole calling period and make any final tweaks.

You can look do a search for sample scripts here on the WF from people like Jason Kanigan, John Durham and others. Use the examples they give and then craft a script that fits your unique style and personality.

In my opinion - You should tweak it as you go along if it's not working. Your best bet is to have a BASIC short script with the least info possible (and learn that), then you talk around it in a conversational way. So you can add or remove things, or say things differently as they come at you. If you've learned this long, robotic script, you will have a tougher time changing it up to fit your calling campaign.

Here's a sample...you can see it's pretty direct, by asking for an email and an appointment within the 2nd line. Of course, it's for appointments, but can be tweaked for other use, and you can always add in your qualifying questions.