When I first started blogging, I assumed that the labels/tags you added to your blog were like keywords. So I would pile on every single keyword I could think of that might have been related to the post in an effort to have Google make my blog come up as a number one hit.
It actually took me a really long time before I started to figure out what they were really for. Now I'm not saying that the labels don't affect internet searches. The Google algorithms for relevant material on searches are extremely complex I'm sure that labels probably factor somewhere in there. But they're really not for the searches. The labels are actually for your blog.
When you get people to your blog, you ideally want them to read more than just your newest post. Number of views does affect search engines. Every time someone views a post, the post becomes more relevant. So if someone types in "apple pie recipes," a post that has had 10,000 views and 50 comments will rank higher than a post that has had 1 view and no comments.
So you want to try and get the most out of all of your posts, not just the newest ones. This is where the labels come in. Think of the labels as file folders more than keywords. If you write a blog post that is part of a series, you would want to give it a label/tag. So if you write your apple pie post, maybe add the label "pies." Then when you write another post the next week about key lime pie, you can add it to the "pies" label as well. What this does is allow the reader to click on "pies" and then see every single post you've ever made about pie.
So only add labels that you know you'll probably have multiple posts for in the same category. Labels can make searching your blog very easy but they can also be a distraction if you have too many labels. A blog post with fifteen labels at the bottom and all the labels only having one post each in them is not going to help readers find your other work.