The most simple way is to disable button  after click. To do this, add JavaScript event "onclick" like below:

<form>
<input id="submitButton" type="submit" value="Button" onclick="disableButton()"/>
</form>

<script type="text/javascript">
function disableButton()
{ document.getElementById("submitButton").disabled = true; }
</script>

If you need framework specific solutions, please let us know which framework do you use.
For example Struts2 has tokens to avoid this situations.