PageRank sculpting with the nofollow attribute used to be all the rage until Matt Cutts shut the door on it almost two years ago. The upshot of this was that you could still use nofollow on links that you didn't want to vouch for, and no PageRank would be passed to them, but the nofollowed link would still consume PageRank.
In other words, nofollow wasn't a way to control the allocation of PageRank from the pages of your site.
Once Cutts made this clear, sites that were using nofollow to sculpt their site PageRank quickly began to remove the nofollow links. Many of these abandoned the idea of PR sculpting altogether. However, there are many ways in which sculpting can still be done.
PageRank, as defined in the original Sergey-Brin thesis, doesn't correctly capture the broader concept of "link equity." Link equity is the concept of the influence of links on a pages ability to rank for particular search queries. Link equity takes into account things like relevance, authority and trust, link placement and accessibility, the positive value of relevant outbound links, and the like.
Just as we used to with PageRank, you can think about allocating link equity within your site. Each site and each page on a site has link equity to allocate. You can think of this allocation as "sculpting."
Here are a few ideas on how sculpting can still be done.
1. Look at Your Footer
Amazon.com has four links under Get to Know Us, five links under Make Money with Us, and five links under Let Us Help You, for a total of 14 links. This means that every page of the site has 14 links to these pages. Granted they are important pages that many users will want to access.
However, Amazon probably doesn't care if they get Google traffic for the phrase Investor Relations. Amazon could potentially collapse these 14 links into three pages using the headers for each as the page name. This would reduce the link drain from 14 internal links per page to three. This focuses more link equity on the other pages (the money pages!) of the site.
2. Flow Context
Well organized site architectures provide strong linking patterns between related pages. Think of this as reviewing the relevance of the links on each and every page of your site. Pages that link to unrelated stuff lose some of their link equity because they lose some of the strength of their own relevance score.
To provide a simple illustration, imagine a page with eight links to other pages on the web, and let's say that prior to any adjustments that the page has eight link equity points to vote. Let's say that four of the links are outbound links to quality relevant pages, three are to relevant pages on the site, and one is to a low relevance page on the site. Traditional link equity theory would hold that each of the eight links passes one link equity point.
However, linking to low relevance pages is likely to cause an adjustment into how the page is able to vote for other pages. The relevance score of the page (a significant factor in my expanded definition of link equity) is reduced by the low relevance link, which means it has less value to pass to the other pages of the site. Simply, the one link to the low relevance page may effectively reduce the passable link equity points from 8 to 7.5.
3. Eliminate Duplicate Content
It's important to have a clean site architecture organized into logical categories. For example, you may have a vehicle insurance site with four major categories of products: auto insurance, motorcycle insurance, RV insurance, and boat insurance. This might represent one navigation tree on the site.
You may also have navigation by state, since coverage tends to vary by state for this type of insurance product. That may be a separate navigation tree. Then you may also have pages for Florida auto insurance, Florida motorcycle insurance, Texas auto insurance, etc. You may be able to access these pages from the product category pages as well as the state pages.
Be careful here. You don't want to have both http://www.yourdomain.com/florida/auto-insurance and http://www.yourdomain.com/auto-insurance/florida on your site. Duplicate content squanders your link equity. Eliminate it, and you're off to a good start.
4. Have Distinct Titles for All of Your Pages
The single most important factor for your page's ability to rank for a given search term is the page title. As a result, when you have two pages with the same title, they will compete for the same search terms. Yet, Google often doesn't want to show more than one page on the same site for a given search term. This ends up being similar to the duplicate content issue.
Make sure that each of your pages have titles that express a unique and distinct concept (for example, "putter" and "left handed putter" and "Ping left handed putter" all work). Just another step toward effective management and distribution of your site's link equity.
5. Eliminate Low Quality Pages
Low quality pages don't pass link equity well. Obviously, pages that aren't indexed don't pass any link equity. Further, pages that aren't crawled often won't have new links discovered often.
However, it goes quite a bit deeper than that.
For example, pages with small amounts of unique text, and perhaps with just an image or two, and that have no links from external sites, are low quality pages. They may be indexed, but that doesn't mean they pass link equity well at all.
In fact, if the page is viewed as poor quality, they may pass little or no link equity. Even if the Google Toolbar says it has a PageRank of 4 (which may lead you to believe that the page has link equity), the practical value such pages have in passing link equity to other pages may be effectively zero anyway.
6. Let the Search Engines do it For You
Face it, they probably filter your footer anyway. They try to sort out duplicate content and adjust.
Items 1 and 3 are things that the search engines have their own reasons for trying to resolve. They will only get better at this over time.
I don't love this solution, but I offer it for completeness. Here, you're depending on the effectiveness of a third-party software program (the search engine crawler) to work correctly on your site.
The first two items relate in the traditional sense to what people think of as PageRank sculpting -- directing the search engines on where to send the juice. Instead of an artificial construct, such as the nofollow attribute, you instead direct the sculpting through the way you implement the links on your site. For the great majority of sites this should line up well with the things you want to show your users.
The duplicate content cleanup and page title efforts are really about eliminating the squandering of link equity. But, when you do this, what you end up doing is sending less link equity to pages that you don't want to rank, and more to pages that you do.
Eliminating low quality pages is related -- low quality pages can't rank effectively and don't pass much link equity back to the other pages of the site. As a result, you may have links on those pages that are intended to pass link equity to other pages on the site, but don't actually do so.
Address these issues effectively, and you can have a significant impact on rankings and traffic. Great way to start the new year!