When teaching computer novices I notice that some always double-click when it isn't necessary or they ask 'How do I know when to single-click verses double-click?'.
I've been using a computer for so long that I don't even think about whether to single or double-click which makes it difficult to explain. I can give novices rules in specific instances like 'Almost always single-click when using a web browser'. However I can't think of any generic rules or suggestions to give them.
It varies somewhat based on context and operating system, and the behavior can be redefined through settings or expanded by applications or utility software. As general rules for default operation:
Things that are, or act like, hyperlinks, or controls, like buttons, operate with a single click.
For objects, like files, one click selects the object. Double click executes the object, if it is executable, or opens it with the default application.
However, the mouse controls can be optionally set to select just by hovering and open/run with a single click. That's a matter of personal preference.
Some applications software define additional, specialized uses for double click. For example, double-clicking on text in some word processors selects a predefined amount of text, like a word. Excel and some other spreadsheets define special operations that can be done with a double-click depending on where it is done. For example, double-clicking on a row or column boundary will resize automatically to accommodate the row or column contents.
Those kinds of specialized uses for double-click are more in the nature of features of the software that you learn. In many cases, they have been adopted by competing applications so you will find that they often work when you switch software.
The cursor (the little image on the screen that moves in relation to your physical movements when manipulating the mouse's planar orientation against a flat surface) tells you a lot about what it's on-top of.
For the large part, a single click is all that's required, unless opening files.
The default arrow means if you click (depress the large button on the left side of the mouse) once, the thing behind the cursor will be selected. In geek-speak, we say the object has focus. If you double-click (depress the left mouse button twice in rapid succession), you will activate the object's default action. With files, this is generally "Open". Messages, options and menus (like "OK" and "Save") only require a single click.
When the cursor is a hand with a pointing finger, it signifies that you are over an interactive object, such as a hyperlink. These only require a single click. It's rare that double-clicking is required when browsing the Internet.
When the cursor is an I-bar, it signifies that the cursor is over a text field.
Click once to activate that field and begin typing to enter text.
If you want to know what actions are available or intend to select an action other than the default one, right-click. This will invoke what's called a "Context menu". It is a list of what you can do with that object. Left-click to select the option you require, or press "Esc" on the keyboard or click somewhere off the list to cancel it.
When the cursor is something rotating or spinning, it generally means the computer is working on something. Patience is best employed here.
Finally, there are other cursors when you use special programs like photo editors or games, that indicate which tool you currently have selected.
Interacting with a computer is a lot like having a conversation. You give a command and wait for a response.
I have been a technology trainer for nearly 20 years, this is a common question and a distinction that is not often clear.
After conversations with many gurus, I have learned the following: 1-The one hard and fast rule when you NEED a double-click is for a desk top icon 2-For everything else click ONE TIME and if you do not see evidence of a response after three seconds, then double click 3-Multiple clicks (like when you get impatient and click happy because you are not getting a response) can cause 'open cursors' in a database which can slow response time or even cause you to time-out.
My rule of thumb is that if an icon has a checkbox it will need a double click. (which incidentally is the first use I have found for the checkboxes)
I've taught my dad the difference using the following rule of thumb;
If an action needs to be performed (like opening a folder, or playing a movie) always double-click.
If you're looking for operational options or additional actions to perform such as bring up a context menu for a file, or just the desktop context menu, right-click.
It's worked for him and he doesn't get it wrong ever.
