I’m a new player. My biggest hurdle seems to be getting false tones, for lack of a better term. If I’m playing any note, I might get the note an octave higher, or somewhere in between. What’s the secret to overcoming this?
the secret would be breath control - and practicing it untill you get the hang of it 
Playing the whistle is much fun - also learning it.
I wish you the best 
Indeed, the secret is breath control. But be advised that some whistles require much more of it than others. Beginners do well with Sweetones, Megs, Burkes and some other whistles that are a bit more “forgiving”. Other whistles, such as Gen and Feadog, might frustrate you due to their demands, but have charms that make your extra efforts worthwhile.
Thanks for the tips. I’m starting on a Waltons tweaked Mellow D. Is this a good beginner instrument?
Walton’s was my first whistle
and I still love it.
it’s a good start
Another cause of squeaks is failing to seal the holes completely. I sometimes miss a hole and get a squawk. Breath control is the most important thing to learn.
Ron