I've been growing chillies for some years now, mostly in a greenhouse, and find they sometimes start off slow but once the weather warms up they burst into growth. Have overwintered a few indoors - a numex twilight which is fruiting again now after basically being more or less ignored all winter in the front room then had a good trim back and feed with chilli focus.
I try different varieties each year, and there is a big difference in size of plant/growth etc. For example Friars Hat grow tall - 3 or 4 foot easily in a medium size pot - whereas habanero types are a more compact grower and later fruiting.
Each year I have several that I leave as 2 plants in a pot - and this seems to make little difference in their growth. I'm quite conservative on pot sizes too as I find putting them in too big a pot seems to have a negative effect sometimes - and use perlite/vermiculite in reasonable proportions to compost. I sometimes pollinate them with a small paintbrush - probably not needed but feels like you're helping
By no means an expert, but it seems to me you can't go too far wrong with chillies somewhere warm, sun, feed occasioanlly, leave them to be more dry than wet as Fleurisa said. They're very rewarding when you get a pile of fruits and grind your own powder!