This is Controller example how to override New button, and provide some default value for Name field and Record Type selection in salesforce.com

NewQuotationController.java

// transition page to create new page with default Name field
public class NewQuotation_Controller 
{
  
  public NewQuotation_Controller(ApexPages.StandardController controller)
  {
    //CreateNew();
  } // constructor
  
  // function to process
  public Pagereference CreateNew()
  {
    String strObject = 'Quotation__c';
    String strPrefix = Schema.getGlobalDescribe().get(strObject).getDescribe().getKeyPrefix();
    System.debug('DEBUG: prefix ' + strPrefix);
      // get record type
    String strNewPage = '/' + strPrefix + '/e?Name=Autonumber&nooverride=1';
    
    String idRecordType = ApexPages.CurrentPage().getParameters().get('RecordType');
    if (idRecordType != null) strNewPage += '&RecordType=' + idRecordType;
    
    Set<String> setParams = ApexPages.CurrentPage().getParameters().keySet();
    String idOpp = '';
    
    String strOppPrefix = '';
    String[] arrTmp;
    /*
    for (String S: setParams)
    {
      if (S.contains('_lkid')) 
      {
          idOpp = ApexPages.CurrentPage().getParameters().get(S);
          arrTmp = S.split('_');
          strOppPrefix = arrTmp[0];
      }
      // System.debug('DEBUG: S = ' + S);
    }
    if (idOpp != '')  // search default opportunity, account and contact
    {
      for(Opportunity_Custom__c O: [SELECT Id, Name, Account__r.Name, Contact__r.Name FROM Opportunity_Custom__c tunity WHERE Id = :idOpp LIMIT 1])
      {
        idOpp = O.Name;
        // TODO : find default for account and contact
      }
      strNewPage += '&' + strOppPrefix + '=' + idOpp;
    }
    */
    //System.debug('DEBUG: ' + strNewPage);
    PageReference newPage = new PageReference(strNewPage);
    return newPage;  
  } // function
  
   // test method
  public static testMethod void mySelfTest()
  {
    Quotation__c  objQ = new Quotation__c(); 
    ApexPages.StandardController tmpPage = new ApexPages.StandardController(objQ);
  
    NewQuotation_Controller objC = new NewQuotation_Controller(tmpPage);
    objC.CreateNew();
  }
}