This question have many relevant info.

Generally speaking most browser compatible would be the use of apex:actionStatus . Something like this.

<apex:actionStatus id="saveStatus">
<apex:facet name="stop">
    <apex:commandButton value="Save" action="{!save}" status="saveStatus" rerender="saveParentBlock" />
</apex:facet>
<apex:facet name="start">
    <apex:commandButton value="Saving..." disabled="true" status="saveStatus"/>
</apex:facet>
</apex:actionStatus>

But i personally prefer the use of javascript. This way.

function disableBtns(){
     $j('.btn').prop({className:'btnDisabled',disabled:'disabled'});
 }
 function enableBtns(){ 
     $j('.btnDisabled').removeProp('disabled');
     $j('.btnDisabled').prop('className','btn');
 }
<apex:actionFunction name="saveAndNew" action="{!saveAndNew}"/>
<input type="button" class="btn" value="{!$Label.SaveAndNew}" onclick="disableBtns();saveAndNew();" />

This question have many relevant info.

Generally speaking most browser compatible would be the use of apex:actionStatus . Something like this.

<apex:actionStatus id="saveStatus">
<apex:facet name="stop">
    <apex:commandButton value="Save" action="{!save}" status="saveStatus" rerender="saveParentBlock" />
</apex:facet>
<apex:facet name="start">
    <apex:commandButton value="Saving..." disabled="true" status="saveStatus"/>
</apex:facet>
</apex:actionStatus>

But i personally prefer the use of javascript. This way.

function disableBtns(){
     $j('.btn').prop({className:'btnDisabled',disabled:'disabled'});
 }
 function enableBtns(){ 
     $j('.btnDisabled').removeProp('disabled');
     $j('.btnDisabled').prop('className','btn');
 }
<apex:actionFunction name="saveAndNew" action="{!saveAndNew}"/>
<input type="button" class="btn" value="{!$Label.SaveAndNew}" onclick="disableBtns();saveAndNew();" />