Use If I were you… to say what you would do under the given circumstances. After if I were you…, use would + infinitive.

• If I were you, I would accept that job.
• If I were you, I wouldn’t quit my job.
• If I were you, I would get that lump examined.
• If I were you, I wouldn’t let this happen.
• If I were you, I wouldn’t do that.
• If I were you, I would invest that money in real estate.
• If I were you, I wouldn’t pocket this insult.

To talk about the past, use would have + past participle after If I were you…

Compare:

• If I were you, I would call the police. (Here the speaker is advising the listener to call the police because that is what he / she would do in such a situation.)
• If I were you, I would have called the police. (Here the hearer didn’t call the police, but the speaker says that that is what he would have done in such a situation.)

To give strong advice, use You had better…

• You had better consult a doctor.
• You had better study harder.
• You had better brush your teeth regularly.
• You had better acquire some computer skills.
• You had better get some rest.
• You had better get that tooth extracted.

Another phrase you can use to give advice is Why don’t you…?

• Why don’t you apply for that job?
• Why don’t you see a doctor?
• Why don’t you pay your tax?
• Why don’t you ask for a raise?