This is the part you have to think before doing.All you need to have is a good plan.What is the topic you gonna use??does it attracts the people??So you will have to concentrate about one good topic you are always watch full.Try to create your blog with most popular and what visitors looking for.
Do not enter anything not belongs to your topic because it should be a blog right on target.If you try to have many topics in the blog,visitor will be hesitated and will not find what he wants from your blog.
And also the Elements you are going to use must be match with your blog topic.
To add Elements for your blog,Go to layout section in your blog customization and select add gadgets to your blog.As ex-Slide show , picture , Video etc