How long does it take to get your blog indexed by major search engines like - Google, Yahoo, MSN?
Almost all major search engines automatically index blogs, when they come accross a link to blog while crawling the web. Some good forums related to your blog subject would also help. Simply place a link directing to your blog in your forum signature.
The best way that followed by almost every blogger is to submit your site feed to some niche blog directories. Such as - Technorati, Bloggernity, Blogcatalog, Feedster and other blog-specific search engines. They have different indexing methods and techniques.
Also, if you are using Blogger, make sure your blog settings are setup to 'PING' the weblog update service. There are spiders always hungry for new content.