I'll endorse RotorHorn's comments on Dick Sandford's 1-day safety course. (I seem to remember it being a 2 day thing if you include some flying). Well worth the money! Dick even got me experiencing Rotor-Stall! Yes, we demo'd it, and it was quite sudden & dramatic, even in my '44. OK - don't panic, we were carefully placed in a nice steady 6-inch hover over grass!
...and as for the comments about dumping the lever the second you hear the horn, I'll go for that too.
However, I still remember when I did SFH in a '44 at Cranfield, and the darned thing had a RadAlt, with the threshhold set at 500 feet. So, every time I'm coming on finals, calling on the radio, looking for other a/c, final checks & really busy etc. off goes this horn thingy at 500 ft. Got me every time! Jumped out of my skin & had to override the instinctive desire to dump the lever!
Then again, I suppose I shouldn't complain. I got into this flying thing because it was exciting in the first place! ;-)
Holly_Copter