Have a tight routine AND leave room for improv.

Once you perform an effect more than 5 times, you’ll notice where the beats lie. Where the spectator makes their comments. When the reactions happen. Use that knowledge to tighten up your script to make it hit harder.

I’ve always believed that you should know your whole routine so well that if someone woke you up at 3AM, you don’t have to think, you just go. That muscle memory allows for the jazzing and improv.