Announce the post in the tweet
It's a good idea to announce the tweet with something like "new blog post". Stats have shown that this phrase helps increase the number of clicks the link gets.
The body of the tweet will be the title of your blog post. So, you should already have something clear and compelling here. But there's no reason why you shouldn't rewrite it to make it punchier and pithier for Twitter.
Use good hashtags
Make sure you include appropriate hash tags at the end of the tweet, although you don't want to use too many. Apart form anything else you want to leave enough free space so that the tweet can be retweeted by others in full. That's why having no more than three is a good idea.
It's always worth putting some thought into which hashtags you're going to use. Remember that some of the more general ones are hugely popular (eg, #blogging). So, they may lift your tweet's visibility quite a bit as people search the platform using them, but this effect will only apply briefly as they get buried by all the others.
That's why using more specific hashtags (eg, #bloggingtips, #bloggingstrategy) can be a good option. You'll still get benefits, but for longer.
Images make blog posts themselves more interesting. And the same thing applies on Twitter. A tweet that has a photo, picture or infographic is more noticeable in the stream and ultimately more tweeps will click on the link included than if it is words alone.
Often Twitter will automatically import an image from the post. But if not you'll have to upload it yourself when composing the tweet. If that's the case make sure the file size is small. This makes the process quicker and easier. I usually reduce mine to around 100kb or less.