How To Make Auto Related Post

login into your blogger account.
Select the Layout menu (Layout) »Edit HTML.
Tick ​​the Expand Widget Templates.
Copy-paste the following script above code </ head>.

 

<script type="text/javascript">
//<![CDATA[
var relatedTitles = new Array();
var relatedTitlesNum = 0;
var relatedUrls = new Array();
function related_results_labels(json) {
for (var i = 0; i < json.feed.entry.length; i++) {
var entry = json.feed.entry[i];
relatedTitles[relatedTitlesNum] = entry.title.$t;
for (var k = 0; k < entry.link.length; k++) {
if (entry.link[k].rel == 'alternate') {
relatedUrls[relatedTitlesNum] = entry.link[k].href;
relatedTitlesNum++;
break;}}}}
function removeRelatedDuplicates() {
var tmp = new Array(0);
var tmp2 = new Array(0);
for(var i = 0; i < relatedUrls.length; i++) {
if(!contains(tmp, relatedUrls[i])) {
tmp.length += 1;
tmp[tmp.length - 1] = relatedUrls[i];
tmp2.length += 1;
tmp2[tmp2.length - 1] = relatedTitles[i];}}
relatedTitles = tmp2;
relatedUrls = tmp;}
function contains(a, e) {
for(var j = 0; j < a.length; j++) if (a[j]==e) return true;
return false;}
function printRelatedLabels() {
var r = Math.floor((relatedTitles.length - 1) * Math.random());
var i = 0;
document.write('<ul>');
while (i < relatedTitles.length && i < 20) {
document.write('<li><a href="' + relatedUrls[r] + '">' +
relatedTitles[r] + '</a></li>');
if (r < relatedTitles.length - 1) {
r++;
} else {
r = 0;}
i++;}
document.write('</ul>');}
//]]>
</script>

Find <data:post.body/> code, then copy-paste the following code at the bottom.

 

<b:if cond='data:post.labels'>
<b:loop values='data:post.labels' var='label'>
<b:if cond='data:blog.pageType == "item"'>
<script expr:src='"/feeds/posts/default/-/" + data:label.name + "?alt=json-in-script&amp;callback=related_results_labels&amp;max-results=5"' type='text/javascript'/>
</b:if>
</b:loop>
</b:if>

<b:if cond='data:blog.pageType == "item"'>
<h4>Related Post</h4>
<script type="text/javascript">
removeRelatedDuplicates();
printRelatedLabels();
</script>
</b:if>

 

Save the template.