make a mountain out of a molehill: make something seem much more important than it really is.
"Calm down. There's really nothing to worry about.
You're making a mountain out of a molehill."
make up one's mind: decide what to do.
A: Where are you going on your vacation?
B: Maybe Canada, maybe Mexico. I can't make up my mind."
Not on your life!: Absolutely not! (a strong "no").
A: "Someone said you cheated on the test. Did you?"
B: "Not on your life!"
now and then: occasionally; from time to time.
A: "Do you see Jennifer often?"
B: "No, not really. I see her now and then, but not regularly."
nuts: crazy.
A: "Stuart says some really strange things sometimes."
B: "Sometimes? All the time! He's nuts!"