which file should I edit for this?

For example when i used to run kdesktop I simply made a script with the command I wanted to start at startup, and put it in /.kde/Autostart.
Now I switch my desktop- environment pretty often ( each has its own strengths), which I really love doing

So how do I setup startup programs that are user-independent as well as window-manager/environment independent. They should jsut start with X, and be use-specific.
I tried xinit,xsessions but it didn't seem to work . Or was i editing them incorrectly?

The theory is that ~/.xinitrc is used when X is started from the command line (i.e. startx), and ~/.xsession is used when running under a display manager. However, the primary script(s) still has to call/source the file. It sounds like ~/.xsession it not being run.

In Slackware (which also doesn't run ~/.xsession by default), the scripts to start a given windowmanager are in /etc/X11/xinit/xinitrc.<wm>. Of course, that may differ for Kubuntu, but I guess they will be somewhere under /etc/X11. One simply needs to add a line to call ~/.xsession, e.g. put a

before the actual window manager is exec'd.

Still doesn't works
My /etc/X11/xinit/xinitrc
If I manually run "sudo ./xsession " then the apps start.