Are you unsatisfied with 100s of freely available WordPress themes and would like to design and develop, or build, your own WordPress theme. Building or designing your own WordPress theme makes your blog look professional, even if it is a simple, minimalistic theme because even if it is not complicated and stylish, it is unique. You may also like to incorporate your own existing website design into your blog.
In order to design or build your own WordPress theme you will need to install WordPress on your local PC (instead of a remote server) and for that you need a server running on your PC. For that you can install Apache. Aside from that, since WordPress is built in PHP and uses MySQL to store your blog content, you will also need PHP and MySQL. You can install all three by installing XAMP. This tutorial properly explains how to install XAMP on your local machine, and how to use it to develop a WordPress theme afterwards.
You can build a WordPress theme either from scratch or use a framework. A framework gives you a basic structure to build your application upon. This blog post reviews some excellent and search engine optimized WordPress theme frameworks.