RDA guidelines

Fewer abbreviations; what were formerly abbreviations are now spelled out UNLESS the abbreviation is transcribed.
Exceptions
- mono and stereo are no longer considered abbreviations
- p and c are no longer valid preceding the date; instead, you'll see ℗ or © (or spelled out phonogram, copyright)
- abbreviations of measurements (cm, in., min., sec., etc) are still allowed.
- Music related numbers (i.e. op., n., no, no., Nr., etc) are left abbreviated.
When there is no publisher information, the records will say [Place of publication not identified] and/or [Publisher not identified].
Dates might look very funny. You might see phrases like "not before" or "not after," or "between YYYY and YYYY].
In general, whenever more than one person or body is responsible for a work, only the first is required in the record. Alternatively, all persons will be listed.
- If only the first of many is listed, that name will be followed by [and ## others].
Not all persons listed need to be traced.
Traced names do not need to be justified in the record.
Parallel titles can come from anywhere on the item.
In general, there is a lot more room for cataloger's judgement; a variety of cataloging choices will be correct according to the rules. There will be a lot you just have to accept as is.

If available, the title on the disc will always be used for the 245, even if a collective title is available on the container.
There is no more $h in the 245. Instead, you will see:

336 performed music $2 rdacontent
337 audio $2 rdamedia [not required]
338 audio disc $2 rdacarrier
"Audio disc" replaces "sound disc."
Encoding information (i.e. CD audio) is now included in 300 $b UNLESS the information is included in $a. Playing speed is now an optional addition to $b, as well.
Examples of different possibilities for the same item

300 1 audio disc (53 min., 45 sec.) : $b CD audio, stereo ; $c 4 3/4 in.

300 1 audio disc (53 min., 45 sec.) : $b CD audio, stereo ; $c 12 cm

300 1 compact disc (53 min., 45 sec.) : $b digital ; $c 4 3/4 in.

300 1 audio disc (53 min., 45 sec.) : $b CD audio, digital, stereo, optical, 1.4 m/s ; $c 4 3/4 in.

Albin O. Kuhn Library & Gallery - Staff Wiki