Got a few tips, off the top of my head -
find proper chapati flour and avoid normal flour; you can use a mix with gram flour but not really necessary.
For the grease, my mum uses rapeseed oil instead of butter
The water - not boiling, but warm
Make sure the dough once kneaded is covered and rested for at least 10/15 mins, but i prefer 25-30 mins,
A key point - when cooking them, you really need a tava/tawa, a frying pan just doesn't work in getting them nice and puffy.
I got a recipe at home, but most general ones say on the bbc website are fine in terms of ratios etc.