Much more information is available in the Emacs online help and in the Emacs manual. This page just gives some brief notes.
How can I enter accented letters not present on your keyboard?
You can type
C-x 8 followed by a punctuation mark and the letter to accent. For example,
C-x 8 ’ e inserts é. The punctuation marks used to specify accents are fairly mnemonic. Here are some of the more common examples.
For more information, type
C-x 8 C-h
How can I enter arbitrary Unicode characters?
C-x 8 RET followed by either the code point in hex or the name of the official Unicode name of the character.
How can I find out information about a character?
C-u C-x = will give information about the character under the cursor.
How can I tell what encoding your file is using?
C-h C RET. (Note that’s an upper case C.) This will tell you the coding system for the current buffer and much more.
How can I change a file’s encoding?
C-x RET f will prompt you for an encoding. You could then enter
utf-8, for example, to specify UTF-8 encoding.