To get an account at a webhost, you'll need an email address. If you have a name already chosen for your site, you might find it easier to keep all your correspondence with your webhost in a separate e-mail account. The webhost will send you an account confirmation, along with any information needed to login to your website control panel.
All of the free hosting services include website creation tools, but if you want to load your own website, and have total control, then a host that allows FTP (File Transfer Protocol) access is the most common account. All of the free webhosts have graphical file managers, as well, but FTP transfers reduce the HTTP overhead of the typical browser transfer. The file managers seem to vary a bit, so an FTP utility, or the integrated FTP function of your web editor might make transfers easier across different hosts.
There's plenty of free hosts that offer accounts that are advertisement free. Advertising that you don't control is a surefire way to kill any traffic to your website.