Slang is highly ephemeral: it changes from one generation to another. Slang terms come into existence for various reasons, some obvious, some inexplicable, but most of them are delightfully direct and to the point. The use of slang adds spice to speech and writing.
Run to it: be enough.
e.g. Do you think the water supply will run to it?
Man of parts: an individual with different accomplishments.
e.g. He is a writer, a painter, and a musician--certain a man of parts.
Pull one's weight: do one's share.
e.g. Everyone should pull his weight if we want the project to succeed.
Rich: absurd; unreal.
e.g. He says he'll work hard from now on--that's rich!
Lump it: endure; bear with it.
e.g .It's too bad if you don't it; just lump it!
Near thing: almost did not succeed.
e.g. He won the race, but it was a near thing.
Clear as mud: obvious.
e.g. I thought everybody knew. It was clear as mud!
Have been had: cheated.
e.g. If you paid $50 for this, you've been had!
Go to pot: be discarded as useless.
e.g. This innovation will soon go to pot.
A bust up: a violent quarrel.
e.g. My wife and I had a bust up last night.
Keep one's countenance: refrain from moving or laughing.
e.g. She was so funny with her jokes that hardly anyone could keep his countenance.
Now you're talking!: talking sensibly.
e.g. It's good to hear your suggestions. Now you're talking! All along you were objecting to the plan!
A look in: chance.
e.g. You can try. But I tell you what: you won't have a look in to get that job.
Go while the going is good: leave while the opportunity is still favorable.
e.g. If I were you, I would depart right now; go while the going's good.
Made man: a successful individual
e.g. After all these years of hard work, he is finally a made man.
Go slow with: don't use too much.
e.g. Please go slow with the sugar; that's all we have left.
A lone wolf: a self-centered person.
e.g. He is a lone wolf, and never seems to get along with anyone.
Keep someone sweet: keep someone satisfied.
e.g. He is very good at keeping his boss sweet; that's why he can hold on to his job for that long.
Learning a language takes time and effort, especially if it is not your first language. Even if it is your mother tongue, you still need time and effort to master it because almost every language has its own slang and colloquial expressions, and the English language is no exception.
Language is forever changing. What is currently acceptable or popular may be replaced by something else in years to come, and the use of slang is a strong testament to that. Slang is just an alternative way of saying something. It is sometimes hard to identify what is slang and what is not. Slang and colloquial expressions are often acceptable in informal writing because they are used in communication in movies, newspapers, radio, television, and other mass media The more you learn, the more you will know when to use or not to use them in your formal writing. No matter what, knowing these common everyday expressions is a plus for all ESL learners.