“umlaut” in Latex using inputenc

Some Latex editors (like WinEdt) internally convert your umlauts to Lamport’s umlaut format, e.g. ä \"a
Now, if your editor is not doing it automatically (like Vim 🙂 ), you basically have two possibilities

1. Use Lamport’s umlaut format: \"{}
2. Use a package that can handle umlauts and all characters having a code > 127

The inputenc package:

The inputenc package recognizes all characters that have an ascii code > 127 and hence is able to parse umlauts:

\usepackage[option]{inputenc}

The following options are available and have to be used depending on your operating system:

• latin1/latin9: Most Unix system and VMS.
• applemac/macce: Older Mac systems/current mac systems
• ansinew: Used on Windows, similar to latin1.
• cp437de: MSDOS.
• cp850: OS/2 and with MSDOS, if the codepage IBM-850 is explicitely used.
• utf8: Can be used on most systems (e.g. all newer Linux distributions).

Difference between latin1 and latin9:

The ISO latin9 character set replaces a few less commonly used characters with characters that gained importance recently. If you need the euro sign € or Caron (háček), which replace e.g. the broken vertical bar (¦) or encoded fractions.

Source: http://www.cs.tut.fi/~jkorpela/latin9.html