In the sidebar of the Tasks page, there is a filter called Responsible person. There you can select to have displayed the tasks assigned to anyone, or only to a certain person, including you.

The list of completed tasks appears after the list of incomplete ones for each group and contains only the recent ones. If you want to see all the completed tasks for that group, click on the "Show all completed tasks" link below the ones displayed.

Please note that completed tasks are displayed only when viewing a single project's Tasks page and not when listing the tasks for multiple projects.

When you assign a task to a colleague, the "Send email notification" check-box appears, already checked. If you leave it like this, immediately after you save the task, your colleague will receive an email informing her/him of this new task for her/him.

No email is sent if the check-box is unchecked or if the colleague configured her/his account not to receive email notifications.

You may group tasks by milestone, by assigning the tasks to that milestone. This means that you will have a better view for what needs to be done until that milestone is due.

The comments are very useful for you and your colleagues to discuss about a specific task without changing its contents. If you agree on another perspective of the task, you may mark this one as completed and open a new one with the modified version.

It's advisable not to delete the old task, so you can keep the history of the discussion.