While there are a few ready made themes available for Jekyll, if you want you site to be different its not too hard. Here are some tips to make it easier.
Setting a custom URL
If you create a page called about.html and you want yoursite.com/about to point to this page, without the .html extention. All you need to do is put a permalink in the yaml front matter:
Custom post types
If you want to create sections on your site like Projects, Gallery, Notes, etc in a different list then your blog, you can set custom metadata for instance category in the yaml front matter and create a page that loops over all posts but only shows the ones you need.
This example shows pages, but it can be done with posts as well. You can even create subfolders in /_posts to make it easier to organize.
Truncating HTML content
Suppose you are listing all the posts on your blog index and want to truncate html, Jekyll will give you a parse error due to invalid html. TruncateHTML plugin comes to the rescue.
Discarding HTML tags
If you want to do the same as above but don't care about html formatting in your content, and easier way to do this is