Someone asked me recently about the wisdom of posting the first chapter of her book on her website. I replied: Sounds good to me. Little risk. I don’t know if I’d upload exactly one chapter. I’d find a really exciting place to end the upload–creating a cliff-hanger and leaving the reader dying to find out what happens. Many new writers end a chapter at the logical point, instead of the page-turner alternative.
For example, don’t start a chapter with the protagonist starting out to go somewhere and end it when he comes back. That’s pointless. Begin it with him already at his destination, get him in big, big trouble, then end the chapter. Save getting him out of trouble for the next chapter. Do this often enough and you can keep your readers up until 2 a.m.
“Art is knowing when to st….” –Damson Greengage Satsuma
jguentherauthor 
Sounds like sound advice and very sm…
“Some don’t st…until they dr…” –Damson Greengage Satsuma
I am told ( a little late ) that posting a sample chapter or two of a published book has absolutely no effect on the sales of that book. From practical experience, I would now have to agree.
It certainly doesn’t hurt. And it won’t help much, either, unless the chapter reaches a lot of people who are in the market for a book of that particular type. I suspect if one chapter doesn’t hook the reader, a second probably won’t either. It is important to use a chapter or partial chapter that ends at a point of suspense, of course.