Belajar SEO today will focus with two topics that more into on page optimization technique. I do hope this blog can give more info to you rather just joining this blog for the contest with the keyword term of "Belajar SE0".  I will focus on with SEO tips as below

1. Number of keywords that should have on a page

This is hard to say. But for sure, you cannot spam your blog with too many keyword repeating all over the place. I think the keyword should be appear  not more than 6% of your total sentences. If possible, do not include the keyword in the same sentence. Make sure you reserved that keyword for another sentence and it look like more natural.

2. A keyword density
2.1.3 Keyword density and seo
  The keyword density also play a major roles in onpage optimization. Like i mention to you earlier do not spam your blog with too many keyword as is will not give you any better in your SEO optimization. Sure you may think search engine will say you have something here, but believe me, search engine will penalize your blog by doing spam blog or spplog.