You can place adsene below post title by inserting adsense code first in every posts. When you are writing, you shouldn't forget it. It's possible, but it seems not fancy.
Yes, you don't need to do it. Just once insert adsense cone into proper location in your blogger HTML template.
First, you should get adsense code from your adsense account. I recommend 336x280 or 300x250 rectangle unit for best result. When you get code, you should convert it the escaped code so that Blogger interpret correctly. Use this site.
When you are ready, just follow simple steps.
1. Sign-in your blogger account.
2. Go to Dashboard << Design << Edit HTML
3. Backup / Restore current template (use button in top of the showing page). Whenever you changes the HTML template, DO Backup before begin.
4. Check the 'Expand Widget Templates' box (in top-right of the template script box)
5. Find following code using the find function of your browser(in most case, ctrl+F). You can just look up the codes to find it.
6. Finally, insert following code just above the line you found (above <data:post.body/>)
the conditional tag <b:if...> and </b:if> will make the adsense appear only on post pages. If you want the adsense to appear on all pages, just remove the two lines.
Good Luck!
5. Find following code using the find function of your browser(in most case, ctrl+F). You can just look up the codes to find it.
<data:post.body/>
6. Finally, insert following code just above the line you found (above <data:post.body/>)
<b:if cond='data:blog.pageType == "item"'>
place your escaped adsense code
</b:if>
place your escaped adsense code
</b:if>
the conditional tag <b:if...> and </b:if> will make the adsense appear only on post pages. If you want the adsense to appear on all pages, just remove the two lines.
How to Insert Adsense Just Below Post Title in Blogger