Which attribute should be used to provide a hint or label for an input element in HTML5?

The attribute that should be used to provide a hint or label for an input element in HTML5 is the "placeholder" attribute. Here are the steps to use it:

1. First, you need to create an input element. You can do this by writing <input> in your HTML code.

2. Next, you need to specify the type of input element. For example, if you want the user to enter text, you would write <input type="text">.

3. After specifying the type, you can add the placeholder attribute. The value of this attribute will be the hint or label that you want to provide for the input element. For example, if you want to provide the hint "Enter your name", you would write <input type="text" placeholder="Enter your name">.

4. Finally, close the input tag. Since it's a self-closing tag, you don't need to add a separate closing tag. The final code will look like this: <input type="text" placeholder="Enter your name"/>.

So, the placeholder attribute is used to provide a hint or label for an input element in HTML5.