How to write a DeDuping for Lead or Contact Object.

In this scenario to avoid duplicate email in Lead or Contact object.

I have two object one is standard object and another one is custom object here my question is I am create a new record standard or custom its clone of another record. How u can implements this one.

trigger CloneRecOnAccount on Account (after insert) 

{

list<Account> setAccList = new list<Account>();

set<string> accNameSet = new set<string>();

for(Account newAcc : Trigger.new)

{

accNameSet.add(newAcc.name);

}

list<Account> getAccRec = [ select name,TimeStamp__c from Account where name in : accNameSet];

for(Account getAcc : Trigger.new )

{

if(getAccRec.size() < 2)

{

Account acc = new Account();

acc.name = getAcc.name;

acc.TimeStamp__c = getAcc.TimeStamp__c;

setAccList.add(acc);

}

}

insert setAccList;

}