Hi Pixidou.
I hav found myself in your position many times, and wish i was as well organized as ADSohr.
One thing that i have found helpfull is using frame numbers as file and video names.
If i'm rendering frames (eg) 1-100, i name the clip '1 100', and save the .an8 file as '1 100' as well.
If i need to fix and re-render, i name it '1 100fix1.avi', and same with an8., then fix2, fix3 etc..
I keep doing this till i have it right, then name the final render '1 100FNL' (FINAL) and same with an8.
The vids end up in video editing software, so i look in there to see what files i am using.
If the video clip has the same name as the anim8or file then i know to keep both.
That sorts out video clips and anim8or files.
As far as textures go, have a main texture folder and keep 'ALL' textures in there. (thats every texture that you ever have on your PC!) You can keep textures in your project folder, and if you ever lose any, you know you can find a copy in the main texture folder.