In btc mining, miners should guess a nonce that produce the right hash.
I just want to know the way of guessing.( in btc-wallet or in cgminer).
Does it begin with 0 and continue the increment(+1).
If I was writing a mining program, that's how I'd do it. There really isn't any benefit that I can think of for starting at any other number.
Does it just initial a random number and randomly change it.
That would work, but I don't see why you'd do it that way. Then you'd have to keep track of all the random numbers that you already tried so that you wouldn't waste time trying them again.