I agree with Niliac, children understand more than they let on. I always worked on the belief that if I half expect a certain behaviour they will produce it, ie if I expect my 1 yr old to have table manners they very soon will.
Same went with reasoning, I would just talk that way, "you need to pick up your books so you will be able to find them next time" "you need to put your bike away so daddy doesn't run over it" " don't climb on the table because you might fall off, sit on the chair instead"
DouDou also made a good point with children reacting better to "do ...." than "don't do ..."
Also with the time out corner get a timer so she knows how long she has to stay there.

Have fun, you are coming up to a very trying time.