1) Set up your development environment - Make sure you have two browsers open, one in Incognito/Private browsing mode such that you can see changes to users who are not logged in.
2) Login and create a main page, this is a basic page and will be called something like node/1. Via Configuration -> Site Information you will need to set it as a home page (set the other options while you are here).
3) Change the theme to Bartik in Appearance and then click settings to customise your colour scheme and default icon (note that icons need to be the correct size).
4) Go to People and then click the Permissions tab. Make sure that all users can search your site. Your can then add the search block (via Structure -> Blocks) to the header (or other) section of your page.
5) Go to Structure -> Menus and click "list links" against "user menu". Then click add link and add a Login link with the url user/login and enable this. You can do the same with the url user/register to get a registration link. Refreshing the non-logged in page should now show these links at the top right. Turning off registration can be done via Configuration -> Account Settings.
6) From Structure -> Blocks create a new block with the following content and add it to the header section of your page:
This should set you up a basic and usable site.