The goal, of course, is to have people click on the link so they can visit and read your blog post, so you need an compelling headline and an interesting image. If you're using Blogger, like I am, once you publish a post, it gives you an opportunity to share, just click "share". I've been experimenting with how much to share on the Google+ page and sometimes I include the little descriptive blurb and sometimes I don't. Remember if you give too much away, there is no reason for them to visit the blog. If you don't give enough, well, it's the same reason. You have to just be perfect, I guess!
The other place to promote your blog depends on where your target audience is. This blog promotes my company, BradHallArt and so I also post on Linkedin. If you're writing about gardening, post the link on the gardening forum that you visit. Remember that if people have respect for what you are saying, they will want to read more. If you twist their arms and give them an obvious "sales pitch", they will be turned off. Well, wouldn't you?
Now, go write something that people want to read, keep it short and to the point, include an image, and check the spelling. Then go promote it!