Hi,

I am new to visual force. and i am looking for help with the following task.

I have the following code for a visual force page which has two picklists.

<apex:page standardController="Quote" extensions="SelectionExtension" showHeader="true" sidebar="true">
    <apex:form >
    <apex:pageMessages />
    <apex:pageBlock title="Select Billing Type and Price Group">
        <apex:pageBlockButtons >
            <apex:commandButton value="Save" rendered="{!quo!=null}" action="{!save}"/>
            <apex:commandButton value="Cancel" action="{!cancel}"/>
        </apex:pageBlockButtons>
        <apex:pageBlockSection >
            <apex:selectList value="{!billingCode}" label="Billing Type" size="1">
                <apex:selectOptions value="{!availableBillingTypes}"/> 
                <apex:actionsupport event="onchange" rerender="priceBookList" />
            </apex:selectList>
            <apex:selectList value="{!priceGroup}" label="Price Group" Id="priceBookList" size="1" disabled="{!availablePriceGroups.size=0}">
                <apex:selectOptions value="{!availablePriceGroups}"/> 
            </apex:selectList>
        </apex:pageBlockSection>        
    </apex:pageBlock>
    </apex:form>
</apex:page>


The picklist values Billing Type and Price Group(dependent picklist) is retrieved from the following class through dyanamic soql

public with sharing class PriceGroupSelectionExtension {
    public Quote quo{get;set;}
    Map<String, List<Billing_Client_Type_Price_Group__c>> billingTypeToPriceGroupsMap {
        get{
            if(billingTypeToPriceGroupsMap==null){
                List<Billing_Client_Type_Price_Group__c> billingTypes= [SELECT Billing_Client_Type_Code__c, Billing_Price_Group_Code__c, Billing_Price_Group_Code__r.Name from Billing_Client_Type_Price_Group__c
                                                                        where Billing_Client_Type_Code__c!=null and Billing_Price_Group_Code__r.Hide_In_ICE__c=false];
                billingTypeToPriceGroupsMap= GroupBy.strings('Billing_Client_Type_Code__c', billingTypes);
            }
            return billingTypeToPriceGroupsMap;
        }
        set;
    }

    public SelectionExtension(ApexPages.StandardController controller) {
        Id quoteId = (Id) ApexPages.currentPage().getParameters().get('Id');
        if( quoteId==null){
            ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'You must access this page from a quote'));
        } else {
            this.quo=(Quote) controller.getRecord();
        }

        if(illegalURLs()){
            ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'The website link provided leads to an unexpected page, please close this page'));
        }
        billingCode=availableBillingTypes.isEmpty()?null:availableBillingTypes[0].getValue();
    }

    private Boolean illegalURLs(){
        if((ApexPages.currentPage().getParameters().get('retURL')!= null && 
                !ApexPages.currentPage().getParameters().get('retURL').startsWith('/'))
            ||(ApexPages.currentPage().getParameters().get('cancelURL')!= null && 
                !ApexPages.currentPage().getParameters().get('cancelURL').startsWith('/'))
            ||(ApexPages.currentPage().getParameters().get('saveURL')!= null && 
                !ApexPages.currentPage().getParameters().get('saveURL').startsWith('/'))){
            return true;
        }
        return false;
    }

    public String billingCode{
        get;
        set{
            billingCode=value;
            refreshAvailablePriceGroups();
        }
    }

    public String priceGroup{
        get;
        set{
            priceGroup=value;
            if(billingTypeToPriceGroupsMap.containsKey(billingCode)){
            quo.Price_Group__c = value;
            quo.Solution__c = GroupBy.ids('Billing_Price_Group_Code__c', billingTypeToPriceGroupsMap.get(billingCode)).get(value)[0].Id;    
        }
        }
    }

    public List<SelectOption> availablePriceGroups{get;private set;}

    public List<SelectOption> availableBillingTypes{
        get{
            if(availableBillingTypes==null){
                availableBillingTypes= new List<SelectOption>();
                for(String billingTypeCode: billingTypeToPriceGroupsMap.keySet()){
                    availableBillingTypes.add(new SelectOption(billingTypeCode, billingTypeCode));          
                }
            }
            return availableBillingTypes;
        }
        private set;
    }

    private void refreshAvailablePriceGroups(){
        List<SelectOption> priceGroups= new List<SelectOption>();
        if(billingTypeToPriceGroupsMap.containsKey(billingCode)){
            for(Billing_Client_Type_Price_Group__c billingTypePriceGroup: billingTypeToPriceGroupsMap.get(billingCode)){
                if(billingTypePriceGroup.Billing_Price_Group_Code__c!=null && billingTypePriceGroup.Billing_Price_Group_Code__r.Name!=null){
                    priceGroups.add(new SelectOption(billingTypePriceGroup.Billing_Price_Group_Code__c, billingTypePriceGroup.Billing_Price_Group_Code__r.Name));
                }           
            }
        }
        availablePriceGroups=priceGroups;
    }
    
    public PageReference cancel(){
        if(ApexPages.currentPage().getParameters().get('cancelURL') !=null){
            return new PageReference(ApexPages.currentPage().getParameters().get('cancelURL'));
        } else{
            return new PageReference(ApexPages.currentPage().getParameters().get('retURL'));
        }
    }
    
    I would like to know how to set up a particular picklist value as default in both the picklists.
and also would like to know how to sort these values based on ranking.

Please advise!!