The Gritty Details
Web Form
The web form lets you add little textual notes to yourself. They then show up randomly on your front page. There's a 140 character limit - for best results, make your to-do items small, simple tasks that you can quickly finish and check off.
You can also send tasks in by e-mail. Simply send an e-mail to <your remote key>@whatshallidonow.net, with your task as the body of the e-mail.
You must be registered in order to have a remote key and use the e-mail functionality. You do not necessarily have to send the e-mails from the address listed on your account.
Bookmarklet
The bookmarklet is for when you want to read or respond to a web page later but don't have time to deal with it right now. Bookmark this "Add to To-Do List", and then click it when you want to save a page. You'll have the option to either "read" or "respond" to it later.
Tagging
When you submit tasks, you can click 'More options" and tag them with short words. For example, I like to tag my programming tasks with the language used, the project it's for, and the estimated difficulty. That way, if I really want to work on Python code, I go to http://www.whatshallidonow.net/python/ and only get tasks in Python. Other people have suggested tagging tasks by the time when they need to be performed, or by the place you need to perform them (eg. separate 'home', 'school', and 'homework' tags).
To get tasks with a specific tag, go to http://www.whatshallidonow.net/<tag name>. The same goes for the all_tasks and finished_today lists - append the tag name to narrow down. Tags are meant to be bookmarked - use the browser's functionality whenever possible!
Remote Keys
A "remote key" is like a password, but is intended for use outside of the main site. For example, you use it to verify your identiy to the e-mail functionality, and if we ever add an API, it will be used for that too. You should keep your remote key secret from other people, but 3rd-party client software may need it to do its job.
A remote key is automatically generated when you register, and you can view it at the remote key page.