How many internal links per page should I have, and which ones should be nofollow?
How many links per page is a question that can only be answered depending on each person’s situation. If the internal links add value for your users, they’re okay!
There used to be a rule within the Google Webmaster guidelines which stated to have no more than one hundred links per page, but they have since removed that rule. This goes to show that as far as Google is concerned, the SEO of your page will not be affected for having too many internal links.
One hundred links may seem like a lot if your website is a content driven site, but if you look at very long Wikipedia articles they might easily have three hundred or more URLs linking to other pages. All of those links are useful in directing the user to more information. So, if your internal links are useful, by all means include them on your webpage.
That brings us to the question, which internal links should I nofollow?
As a general rule, you shouldn’t nofollow any links other than links where a bot can’t do anything. An few examples would be, login links, affiliate links, and links to admin areas of your website where the google bot can’t access or crawl. Other than that, I would not nofollow any other links.
On a side note, another great SEO aspect of having internal links within your website is it gives the ability for the Google bot to crawl your website with more ease. The more links pointing to other areas of your website, and being linked together, the better opportunity the bot will have to thoroughly scan your website by following those links to wherever they may lead.