Findings from a usability study with 16 visually impaired people, usefully presented as a set of guidelines. Worth a read to get an insight into how people using screenreaders typically interact with websites and the problems they face.
Guidelines for Accessible and Usable Web Sites: Observing Users Who Work With Screen Readers - by Mary Frances Theofanos and Ginny Redish
PDF version of Guidelines for Accessible and Usable Web Sites
If you've never seen a screenreader in action, here are some examples from You Tube.
Sighted person demonstrating how a screenreader works on a well structured web page
Blind person using her computer with a screenreader (she begins surfing the web at 4:15). Notice how much faster her screenreader reads, compared to when a sighted person is demonstrating. I've done usability testing with visually impaired users in the past and found it almost impossible to take in the information at the speed they listen.
Differences between advanced and novice blind users surfing the web. No two people are the same. Believe it or not, the same goes for those of us with a disability.