1, Speaking it as your character would speak it, adding in phrases they would use, from their own way of thinking - Some characters are wordy some are not. Some are intellectuals, some are not for example.
Basics tips are - Cutting out the fluff if it needs cutting, and adding in more eloquence if it needs it. Trying not to repeat the same words too close together, I know people do in regular life, but you can always just pull out MS Word's thesaurus if you're really stuck.
Usually ends up reading better than it would otherwise.
2, If it's multiple lines do they have a purpose for the character or story, or again are you writing it out as
you think it should sound for filler? If the later you can probably cut it and lose nothing, over thinking tends to confuse scenes and meaning no end. This is harder in an intellectual character or one who speaks many dialogue lines in a post.
Question - What Makes a Good Character Arc, and How do you keep them interesting as you develop your character?
http://en.wikipedia.org/wiki/Character_arc