What is the best advice a lawyer can give to his client who is guilty of an offence?

If the evidence against my client is so strong , then I should advise my client to plead guilty  . 

ask for peaceful way of settlement 

Make a plea of guilt and pray the court for mitigating jugement.

I will try to know from him that he committed that act for aggression and injustice or whether he was forced to commit the sin due to any reason. If he is a transgressor, I will inform him i will not defend him and he has to regret from the victim or his family and try to re-conciliate with them. But if he commits this act in case of weakness, or is forced to do so or in defense of himself, I will advise him that i will defend him for the mitigating reasons or the Minimum penalty of his offence.

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Not to even speak  just   he has not to admit........... and let the  lawyer take care of that case

If he accepts he has committed an offence then two questions arises 1) Contesting the criminal case will depend on the facts which led to the commission of offence 2) Pleading guilty will work only in cases like murder etc not in white collar crime as there is always room for acquital in white crimes.

Plea bargaining will be the best bet. Thanks.

There could be two options. (1) Depending how guilty the client is ? (2) The law in the country where the trial is ? 

Answering the first question: If my client is under trial in a country, where his right to silence flows from a statute, I would suggest he adopt that stratagy.

Answering the second question: If my client has no statutory protection of law to silence, I would suggest going for plea bargining.