I'm glad someone's posted about chappatis. I was going to start a thread - I must've missed this one.
When I started making them, before I knew where or how to get chappati flour locally, I used to use a mix of strong bread flours. My best results came with using 2 parts white to 1 part wholemeal, though I went through all sorts of ratios until I settled on that.
I remember seeing the episode of Michael Palin's 'Around the World in 80 Days' where he travels on the dhow, and it showed the ship's cook making chappatis on a tava over a gas burner. I was intrigued at the way the bread puffed up like a pillow on the tava, without being waved over an open flame.
It's a bit of a dark art getting that to happen in my kitchen, and I always feel disappointed when it doesn't, despite the chappatis being perfectly edible. I can remember a time when I could get that to happen on a regular basis, when I was using the bread flour mix. Funnily enough, it's been harder since I started using chappati flour.
I hadn't made them for a while, until I started posting here again. I bought some East End flour and just couldn't get it to puff up, although the flavour of the chappatis was lovely. Recently I bought a bag of Rajah Gold chappati flour, and had a bit of a breakthrough with it.
What I do is to place the raw chappati on the frying pan and just leave it for a few seconds - maybe 10 - before flipping it over, just to seal it. There are no brown spots at this point. Then I leave it for the standard 30 - 45 seconds or so, until the bubbles start to form in the bread. I lift it up to check that some brown blisters are appearing on the underside. and when they do, I flip again.
Then the thing starts to puff in places, and I've found the best way to encourage it is to press very gently with the back of a fish slice in circular motions, pushing the bubbles out until the whole thing puffs up. This can go wrong very easily; if I burst a blister or crack the surface it's game over, in terms of puffage. But when it goes right it looks like this, as it did last night:

... in which case I dance around the kitchen with joy.

When the chappati's cooked it has the brown blisters on one side, but the other side just looks toasted and caramelised, which is how they generally look when I order them from takeaways around here. It doesn't always work that way, but I can usually get them to puff a bit. I have a gas hob, and can ride the heat as it goes along, but I haven't found an 'ideal' setting. It seems to depend upon the mix and, possibly, how much beer I've drunk when I come to cook them.
I generally cook a bunch of them and fold them in quarters, putting them into plastic food bags 2 at a time. I find they keep in the fridge for 2-3 days easily, with a 30-second blast in the microwave restoring them to their soft doughy glory. I've never tried freezing them.