Preferred apllications and hidden files

[BenTrein]

I've got two noob questions, but I can't find it easily, so I ask here... Forgive me.

First is this:
Whenever I open a file through - say - Open Office, the list of files I get shown automatically also show all the hidden files. Right click -> uncheck hidden files does the trick only for one session. If I hit Open again, they're shown again. How can I set it to not show hidden files by default in the 'open file' dialogue (for all apps)?

Second is this:
Under preferences, there's an item called 'preferred applications'. This is great, and works ok, but is way too general for me. How can I set that files with certain extensions always open with one app, and files with another extension always open with another app.
For example, how can I set that AVI's always open in VLC, but MPEGs in Movie Player. And MP3s with Songbird...

[Dies]

You don't mention what Desktop you're using...

If you are using Gnome, you just right click a file then select Properties -> Open With, select your preferred applications and you're done. You only have to do that once for each file type.

If you're on KDE then you need to look under Advanced in the Control Center then filetypes, just search for the extension and make your changes.

As far as your first question, it sounds like a bug that setting should stick. Of course, Open Office is not really a good example, does it happen with other apps?