The beautiful thing is, you don't need external back links from other sites.
So, you don't really have to leave the home base blog.
The Wikipedia Theory.
Google likes Authority and things that relate to each other. The best way to describe this is like the child's word game that a lot of us used to play. This is when someone would say a random word like "Apple" the other person would say something that would relate like "pie" Apple pie.
That being said, a lot of you have seen the dominate site Wikipedia. Rocking SEO, and always number 1 on the search engines for about any keyword from "Monkey Fighting" to "Under Water Basket Weaving"
(Ok,may have gotten carried away.)
But you get my drift. Notice, how Wikipedia has Anchor text linking to another page of theirs that relates to that topic. Such as a topic about apples and it mentions you can make apple pies out of them.
This would link to another Wikipedia site called Apple Pies which would talk about what type of apples you would need for a apple pie. These would be linked to a page with the target "keyword" in the URL.
The magic happens when Google and other search engines send their Spiders out to index your site for new content, once they have been pinged on a new post or rss feed.
Once there, they read your sitemap.xml (extended markup language) for any new changes and updates their databases. Google loves it when you highlight,bold or underline an anchor text target keyword.
(Caution- You want to make sure you are not over doing it by using the old method of keyword stuffing. Make a decent article with a nice amount of keyword density linking to other pages that have revelent keywords to other internal posts.)
Get a Site Map
I like to say when starting out your own blog always install first Google Sitemap or something that can keep your sitemap updated and send pings to the major search engines. (Wordpress Plugins rock for this.)
When writing posts link to other posts about the keyword topic. Example: apple.html to apple pies.html via anchor text.
It can be difficult to track posts when you get up there in 100's of posts.
But, there are plugins out there that you can get that you can search for certain keywords that you set up in the beginning, and have them link to other internal posts.
I didn't believe this until I saw one of my friends personal family blogs that was not a part of a niche or any monetization.
(He had a Page Rank of 5.)
I used Market Samurai to analyze his back links and my jaw dropped when he had thousands of them coming to domain.
I realized after looking at them, there were all his posts linking to other posts internally. Hardly any back links from external sites.
Think about it and it makes sense in the eyes of Google.
I hope this was informative and when you decide to blog, start internally linking these posts to each other and see if you PR will climb in due time.