So Ruby, you asked about making sure you get people you want to read your blog to read it without getting "spam" (sometimes hackers, sometimes machines that find your blog and attach viruses or spyware, sometimes "trolls" or people that want to cause problems on random blogs). To understand this, it's important to understand some of things you can do with comments and privacy settings.
Comments are very useful to get feedback and have a conversation with your readers. As I mentioned in my previous blog post, it helps you to create a community. However, at least in the beginning, you may want to control who comments and what those comments are. When I first started my blog, I started to get a number of inappropriate comments, often very vague with a link. These are often viruses or companies using your blog to get more people to their blog (the same as those inappropriate "you've won a million dollars" or "enlarge your..." emails you receive (now in your spam folder).
Fortunately, Blogger has a filter like most of your email programs do. But you still may want control over your comments. You may decide you want no comments. This you can do also. Click on your blog "dashboard" (the menu with all your blogs listed). On the left hand side menu, at the bottom is "Settings." Click on it, then go to "posts and comments". Scroll down (move your cursor down)to comments. Now choose which ever setting works for you.
1) Comment Location: If you don't want comments on your blog, choose "hide." This means there will be no comment section on your blog. Otherwise, I suggest using full page.
2) Who can comment? You have 4 choices: the first is anonymous. I suggest you NOT choose this option unless you approve ALL comments first (see the moderation section below). This means you (or google) will have difficulty tracing who has posted the comment. Registered User: This means you can trace back who commented, including an email address and/or profile. User with Google Accounts: This limits who can comment to those with google products. This is especially useful if you are using google + because you can limit outsiders from commenting (but not limiting who can read) your blog. Only members of this blog: There is a setting in which readers can "join" your blog. You have their profile information and can even control who is a member and who isn't. If you use this setting and you want comments, you will need to make sure your readers join the blog first.
3) Comment Moderation: This is the section where you have control over which comments are made public. If you choose "always", then any comment you have on a particular post will show up on you "blog post list" and you will need to click on the comment, then click on "accept" or "delete". This is where I keep my comment settings, since I don't look at my blog post every day. This means if there is an unacceptable comment, it won't be up there for many days or even weeks before I get to it. If you think you're going to be accessing your blog every day, you might want to change the setting to "sometimes" or "never." "Sometimes" publishes all comments within a certain time period (i.e. for posts over the last 7 days). This is helpful if you have readers that may comment on something you wrote a while ago. You may not see the new comment because you only check your most recent posts. You may also want a lively interaction around your blog, with people being able to comment frequently. Then choose "never" and make sure you review the comments and delete inappropriate or "spam" comments that Blogger hasn't picked up.
For those more advanced in blogging, you might want to help your readers comment effectively by creating guidelines for comments. This might include rules of good commenting.