"if you jus' happen to get in trouble like you always done before, I want you to come right here in hide in the brush."
George is telling Lennie to always remember to meet him there in the brush if anything bad happens. Lennie will most likely have to hide there
When George says that Curley's wife seems like a "tramp," Lennie responds that he thinks she is "purty," causing George to warn Lennie to keep away from her, which Lennie will probably not do.
"I ought to of shot that dog myself, George I shouldn't ought to of let no stranger shoot my dog."
Carlson has to put down Candy's old smelly dog. I think that this foreshadows Carlson and the other guys putting Lennie down for George.
Candy feels bad that he had Carlson put down his old friend instead of him taking responsibility for the dog and doing it himself. I think that this will be the case with George in Lennie later in the book, and George will do it himself so he will not make the same mistake Candy did.