There are still web pages that are that annoying. And if you want to make absolutely sure that you are seen as a total scumbag, you will have the "are you sure you want to leave?" when someone clicks away from your annoying page. Needless to say, I don't recommend that you do that.
On the other hand, I do recommend having Google Adsense ads on your blog or website. I'm a graphic designer and a marketing guy, and I do it myself. But there is a right way, and a wrong way, to do it.
By all means, allow Google Adsense on your blog. I am assuming you are using Google Blogger (and if not, why?), so it's pretty easy. You just click a button that allows Adsense and contextual ads appear after each post. And that's really all you should do.
If someone has told you to go into your layout and have the ads at the top, and just generally all over the place, they are recommending that you make a mess of your blog, and make you look like a scumbag. Don't do that.
If you are a little bit more advanced, select the ads yourself. There's a feature in Blogger that allows you to decide what ad to place after your blog post. But you don't have to do that. Google Adsense does its own logic when placing ads, literally "reading" your post and selecting an appropriate ad.
Creating a blog specifically to make money on Adsense is pretty far-fetched. I have four blogs, and several web pages, which get thousands of hits all of the time. As of this morning today, I have made a penny! Still, I guess it's better than nothing.
Just thought you would like to know. I'm experimenting mostly, we're all in this together.