Guided liquid Simulation I am a short movie director and after effects vfx artist and I'm just beginning with the blender vfx game. 
In an upcoming short movie I want to realize a scene where the blood flowing out of a victims head forms readable letters on the floor. I tried a few things with the fluid sim but didn't quite get there...
I'd be very thankful for suggestions on how to approach this.
Thanks, over and out.
I think you are looking for Fluid Control.

I recommend reading the fluid simulation documentation in it's entirety.  It's not long, but covers the topic well and highlights some things to watch out for i.e making sure your obstacles are within the domain.

There are also endless tutorials on youtube and clones.