Being a developer that codes regularly on both Windows and Macintosh platforms, over the years I've found the tools that I'm most comfortable with and have customised them to my liking. Typically, any HTML coding that I do ends up being written in a text editor, on the Mac I use Textmate from Macromates, and on my Windows machines it's TextPad, from Helios software.
TextPad and Clip Libraries
TextPad has a feature called Clip Libraries, which basically is a library of code snippets. Each snippet is identified by a short name and the full code (of the actual snippet). Once the short name is double-clicked, the expanded code snippet is placed at the location of the cursor.
Out of the box TextPad provide a handful of these libraries, such as SMS Texting, HTML Characters, and Control Characters to name but a few.
As I previously wrote, I end up writing most of my code in a plain text editor (rather than a WYSIWYG editor). The other side of the story is that you need to remember all of the available elements of the language, which really isn't terribly difficult for HTML, but when it comes to doctype's I always seem to draw a blank!
When I was to start a new HTML document, and in need of a doctype, I would end up going to a site in one of my bookmarks, viewing source, and copying the doctype. Works most of the time if I got the site correct for which doctype I wanted to use! So, rather than relying upon guess work I ended up writing a Clip Library for HTML doctype's.
Clip Libraries Location
The process is fairly straightforward, and it really only involved a few minutes of tinkering with one of the existing libraries and searching for the doctype's.
Once you download the HTML Doctype Clip Library below simply save the file into the user folder for your clip libraries. You can find this by going to Configure | Preferences menu, then click through to Folders | Clip Library and note the folder path. On my Windows 7 system it's located in C:\Users\serdar\App Data\Roaming\Helios\Textpad\5.0\ and place the file in there. You may have to show hidden files in Windows Explorer to see the App Data folder.
Do not save the file where the default Clip Libraries are, which would be in the Program Files\TextPad\Sample folder, as the next time you restart your machine you'll see that you're custom libraries would have disappeared!