Customer discovery, validate your assumptions as quickly as you can, find very cheap, quick ways of doing it.
Take every opportunity you can learn. Look for massive enthusiasm from the customers that you're talking to about your idea,
and be ready to dramatically change your ideas based on what you're learning for your customers.
And if you want to read more, I would definitely recommend these two books.
They should be the other way around. The Lean Start-Up I read is a good overview of a lot the stuff that we've been talking about here.
The Start-Up Owner's Manual by Steve Blank, who came up with a lot of this theory in the first place, is what it says is it's a manual.
It's a really good book to dip in and out of, to get techniques from and to use to to to point you in the right direction as you go.
So, so go and get those books and my contact details of them.