Here’s what I use:
‘Hi, I’m Lauren, I’m an independent researcher and I wondered if I could ask you a few questions about {whatever this is about – e.g. an airport parking website} in exchange for a {whatever the incentive is – e.g. a £20 Amazon voucher and a coffee}. It’ll only take {however long it will take – e.g. 10 mins max}’.
I’ve introduced myself I’ve stated my intentions clearly I’ve set a time commitment expectation I’ve offered an incentive I always use a friendly, but confident tone. And I always smile. That’s it. Just wanted to share the opener that I always use, and works for me more often than not. Of course, if there is any further qualification of the participant to be done, then it can be done after the above. Don’t forget to identify the right participant targets too.