Best way of archiving?

[StGerolf]

If I want to archive files, is there a rule which type of archive is most eficient for a certain type of file?
Which type of archive should I use for audio and video files?
Which type of archive should I use for .doc and .xls?
Which type of archive should I use for acrobat reader?

[ivan]

The answer definetelly depends on type of files. E.g. some files like MP3 audio files are already compressed (very similar compression to ZIP), so using ZIP definetelly is not propriate for compressing this format. Acrobate readed is also very well compressed, but usually there is something to save even when using ZIP format.

But I suggest you to compress multiple similar files at the same time and use either CAB or 7-ZIP compression. When compressing more than one similar files to same archive using some solid compression, you will get better results than compressing each file separatelly to same archive - CAB is solid by default, and 7-ZIP by option.

CAB is little bit slower, but realible solid compression. CAB files can be easily extracted by any archiver (or even now new installation of Windows XP).

7-ZIP provides much better compression ratio. Ratio and speed of compression depends on file type compressing, but usually with 7-ZIP you can get best ratio than with any other format. It is very good for all of three file types you have mentioned.
One of problems of 7-ZIP is that for extracting it you must have either PowerArchiver or 7-ZIP, but if you use this for your own purposes, then I suggest you to try with 7-ZIP.

[TBGBe]

If you are simply asking which gives the smallest archive file - then I agree with Ivan that 7Zip is usually the answer. However, when I did some sample testing I found that 7Zip was very bad on "compressed" formats such as Jpeg !!

Another consideration may be speed - 7Zip is by far the slowest compression method.
On "normal" filetypes:-
Cab gives the next best compression, usually much faster than 7Zip.
Tar with Bzip2 gives the next best compression, usually faster than Cab.

Note: in my testing 821 Wav files 15,281,041
Bzip2 - about 8 minutes (11.5MB)
Cab - about 25 minutes (11.9MB)
7Zip - nearly 2 hours (11MB)

PS for the Jpegs I tested 10 Files (12,600,516)

cab 7 minutes 12,564,597
bh 3 minutes 12,588,570
bz2 5 minutes 12,615,759 !.expansion.!
7z 45 minutes 12,664,029 !.expansion.!

I would recommend that you do a sample of your own files and judge for yourself.