Hi Alka Ji
Before saying anything on legal aspects, I want you to think thrice before actually taking any such a step because once that Divorce proceedings are started, the last chance of any harmony will get destroyed, irrespective to the fact whether you will get the divorce or not. So please make sure that you can't live with him anymore, before taking any such step, particularly thinking in respect the future of your children.
Now come on the two questions asked by you:-
1. Divorce by mutual consent:-
Section 13-B of the Hindu Marriage Act provides regarding Divorce by mutual consent. If you both decided to take divorce by mutual consent, then both of you have to file a petition before the Distt. Judge for the same. The actual presence of both the parties is must. The court will record your statements and gives you a waiting period of 6 months (minimum). The waiting period is given to think again and tries to make any reconciliation between the parties, if possible. After the given period the parties (both) again appears before the court and told the court that they can't live together and wants to dissolve their marriage. Then after satisfying about the consent being given free without any fear or influence etc., the court passed the decree of Divorce. Court will pass the order regarding maintenance, Guardianship of the children etc. along with it.
Any party can withdraw its consent at any time before the actual decree of divorce is passed by the court. But the pre-condition for applying under this head is that the parties must be living separately at least for the last one year.
It is the fastest & best way to get divorce with minimum bitterness.
2. Divorce on fault of Spouse:-
On the other hand, you can file for divorce on ground of cruelty (mental) under section 13 (1) (ia). In this case the normal court proceeding will follow and you are required to prove the mental cruelty by your husband towards you by evidences & witnesses. This process will take much more time depending upon where you lives, whether special family courts are there or not, and how much work load the court have. If you are able to prove the cruelty by husband in court, then you will get the decree of Divorce. This process will usually takes 2-5 years.
But if one of the party wants to harass the other then by filling appeal in High Court & then In Supreme Court (if allowed), the case may be prolonged even for 15-20 years.