I have created a Visualforce page with a custom controller that is essentially a search page that I've embedded within the Lead page.  It gives my users the ability to quickly search for duplicates without leaving the page.  The issue is, I'm trying to figure out how to prepopulate the search, so they don't have to copy the email address to the search bar.

Here's the Controller:

Public with sharing class LeadOppsearchclas{
 Public List<Lead>leadList{get;set;}
 Public List<Opportunity>optyList{get;set;}
   Public String searchStr{get;set;}
   Public LeadOppsearchclas(){
   }
 
 public LeadOppsearchclas(ApexPages.StandardController stdController){
 }
 
    Public void soslDemo_method(){
       leadList = New List<Lead>();
   optyList = New List<Opportunity>();
   
   if(searchStr.length() > 1){
   String searchStr1 = '*'+searchStr+'*';
   String searchQuery = 'FIND \'' + searchStr1 + '\' IN ALL FIELDS RETURNING  Lead (Id,Name,Email,metro__c,statusname__c,Listing_MLS__c,date_entered_into_Lead_router__c,listing_amount__c,listing_agent__c,referral_fee__c,last_activity_subject__c),Opportunity(Id,Name,Account_Email__c,Opportunity_EMail__c,metro__c,statusname__c,Owner_Name__c,date_entered_into_Lead_router__c,listing_amount__c,listing_agent__c,agent__c,referral_fee__c,last_activity_subject__c)';
   List<List <sObject>> searchList = search.query(searchQuery);
   leadList = ((List<Lead>)searchList[0]);
      optyList = ((List<Opportunity>)searchList[1]);
   if(leadList.size() == 0 && optyList.size() == 0){
       apexPages.addmessage(new apexpages.message(apexpages.severity.Error, 'Sorry, no results returned with matching string..'));
       return;
   }
   }
   else{
   apexPages.addmessage(new apexpages.message(apexpages.severity.Error, 'Please enter at least two characters..'));
   return;
   }
  }
}

And the Visualforce Page:

<apex:page standardcontroller="Lead" extensions="LeadOppsearchclas">
  <apex:form >
  <apex:inputText value="{!searchStr}"/>
    <apex:commandButton value="Search in Lead, Opportunity" action="{!soslDemo_method}"                reRender="lead,error,oppt" status="actStatusId"/>
    <apex:actionStatus id="actStatusId">
                <apex:facet name="start" >
                    <img src="/img/loading.gif"/>                    
                </apex:facet>
    </apex:actionStatus>
  </apex:form>
 
    <apex:outputPanel title="" id="error">
     <apex:pageMessages ></apex:pageMessages>
     </apex:outputPanel>
 
 <apex:pageBlock title="Opportunities" id="oppt">
    <apex:pageblockTable value="{!optyList}" var="opty">
     <apex:column headervalue="Name"><apex:outputLink value="/{!opty.ID}" target="_blank">{!opty.name}</apex:outputLink></apex:column>
     <apex:column value="{!opty.Account_Email__c}"/>
     <apex:column value="{!opty.Metro__c}"/>
     <apex:column value="{!opty.Owner_Name__c}"/>
     <apex:column value="{!opty.StatusName__c}"/>
     <apex:column value="{!opty.Date_Entered_Into_Lead_Router__c}"/>
     <apex:column value="{!opty.Listing_Amount__c}"/>
     <apex:column value="{!opty.Listing_Agent__c}"/>
     <apex:column value="{!opty.Agent__c}"/>
     <apex:column value="{!opty.Referral_Fee__c}"/>
     <apex:column value="{!opty.Last_Activity_Subject__c}"/>


       </apex:pageblockTable>
    </apex:pageBlock>
 
    <apex:pageBlock title="Leads" id="lead">
    <apex:pageblockTable value="{!leadList }" var="lead">
     <apex:column headervalue="Name"><apex:outputLink value="/{!lead.ID}" target="_blank">{!lead.name}</apex:outputLink></apex:column>
     <apex:column value="{!lead.email}"/>
     <apex:column value="{!lead.Metro__c}"/>
     <apex:column value="{!lead.StatusName__c}"/>
     <apex:column value="{!lead.Date_Entered_Into_Lead_Router__c}"/>
     <apex:column value="{!lead.Listing_Amount__c}"/>
     <apex:column value="{!lead.Listing_MLS__c}"/>
     <apex:column value="{!lead.Listing_Agent__c}"/>
     <apex:column value="{!lead.Referral_Fee__c}"/>
     <apex:column value="{!lead.Last_Activity_Subject__c}"/>


 </apex:pageblockTable>
    </apex:pageBlock>
</apex:page>