Well, normally I can tell if I should get rid of the book is if I keep looking at the page numbers or keep thinking of doing something else, not really reading just reading the symbols along the page.
(1)I do not like charaters that do the exact opposite of what they would have done by earlier descriptions of the charater in a certain situation. Unless there was a reason, like somebody with mental powers making the person do something opposite, or the person was indeed acting like he or she would but was an act to fool somebdy.
(2)I do not like authors that repeat themselves; like Arthur C. Clarke saying in every book "even though there is no gravity, there is still mass and inertia."
(3)I do not like authors babying the reader; the said example above or keep saying that there is no sound in space, et cetera.
(4)I hate excessive cussing, it just seems, I don't know, very childish, or dirty or just trying to look "cool." Michael Crichton's Prey is a good example of that, the book would have been very good if it did not have excessive cussing and bad charaters.
(5)I hate stupid charaters; like Eugenia of Nemesis by Asimov, she was supposed to be smart, but she was stupid and always argued over the same thing over and over again, it was repetitive; just like Joanna Stavenger of Moonrise by Ben Bova, that was very repetitive in the arguements and her blaming the moon and the like for Paul's death is just crap.
(6)Bad dialogue, pretty much the result of the 4 and 5; George Alec Effringer's 25 crunch split right on two is a very good example of this, he had an excellent idea of what happened to the guy and the woman and how it turned out, but I could not stand the football parts and the way the charaters spoke: "I don't want no --" "That ain't no --" "I ain't said nothing." "I ain't did no nothing."
(7)Pages of descriptions; very boring if not done right and gets very repetitive, The Once and Future King by T. H. White is a good example, or C. S. Lewis's space trilogy.
(8)Bad metaphors and other ways of describing scenery; I just hate it when they make up stupid things to describe things, Ray Bradbury did it a lot in Fahrenheit 451: "Bang, bang, bang, bang went the lightning" and the like, I hated his descriptions but I really liked the idea of the story.
Various things like that.