I hammer it into my trainees (not literally nowadays!) not to talk to helis until after they touchdown; telling them how busy you chaps are in this phase of flight
This is probably the least busy part of the flight. The non flying pilot is waiting patiently for flying pilot to put it on the ground so he can then do the after landing checks. Switching to "ground" just before landing is great because it gives us a chance to listen out for a couple of seconds before checking in in slow time. The alternative is landing then being instructed to call "ground" at the same time as starting after landing checks then checking in too quickly and stamping on someone just before they read back a clearance or worse, just about to check in to be pipped at the post by "ground" initiating a long clearance and we then have to come to a stop while we wait for the readback.
Feel free to transfer before touching down. We can then either check in with ground straight away or if someone feels they are too busy they can come to a stop and do it in there own time.
Remember many of the more modern helis have the ground freq pre programmed as the next freq so it is just a flick of the switch.
How about "When ready, call ground.......".