Do the checklist before calling for a taxi clearance...
Yes, definitely. Our SOPs have been rewritten many times over the years to try and stop this happening. However, I have been given taxi clearances
before requesting them by keen controllers over the years.
It's the same as ending up on the runway with no flaps for takeoff or lining up without clearance: shouldn't happen but it does, even with the best of intentions and lots of checklists. Multiple distractions can catch even highly disciplined operators...