The more I used it, the more unhappy I became with the us-intl keyboard layout. Especially all the dead keys (keys that may modify the following key e.g. ” + a to write ä) made typing tiresome. Always typing a space after double quotes is really not suited for programming.
I found a good tutorial on writing your own Xorg keyboard layouts:
Creating custom keyboard layouts for X11 using XKB
Using these instructions I created a us_de layout, that uses the us layout and bind alt + a/u/o/s to the german umlauts ä/ü/ö/ß.
To install the file, just copy it to /etc/X11/xkb/symbols/ and edit your /etc/X11/xorg.conf (or type setxkbmap -layout us_de -variant basic into a shell): us_de