
1. Go to Layout>Edit HTML, and look for this line:
</head>
2. Replace the </head> line with whole line bellow
<script type='text/javascript'>var thumbnail_mode = "no-float" ;summary_noimg = 430;summary_img = 340;img_thumb_height = 100;img_thumb_width = 120;</script><script type='text/javascript' src='http://widgets.way2blogging.org/blogger-widgets/w2b-auto-readmore-blogger.js' ></script>
</head>
3. Now search <data:post.body/> and replace with next code
<b:if cond='data:blog.pageType == "item"'>
<data:post.body/>
<b:else/>
<b:if cond='data:blog.pageType == "static_page"'>
<data:post.body/>
<b:else/>
<div expr:id='"summary" + data:post.id'>
<data:post.body/>
</div>
<script type='text/javascript'>
createSummaryAndThumb("summary<data:post.id/>");
</script>
<div style='clear: both;'/>
<span class='rmlink' style='font-weight:bold;padding:5px;float:right;text-align:right;'><aexpr:href='data:post.url' >Read more ... </a></span>
</b:if>
</b:if>
Click Save Button and That's All.
Customizacion:
img_thumb_height = 100; Thumbnail Height
img_thumb_width = 120; Thumbnail Width
Credits: way2blogging