In order to recognize a Japanese promo CD or Vinyl record there are two points to remember: Firstly, know how to read some of the Japanese and secondly, know where to look. It is also worth mentioning that in Japan there are hardly any promotional items rather than Samples which are not for sale. However, those samples are being considered as Promos and sold on Ebay etc.
FIRST, either on the front but usually on the back of the CD case there is a little sticker either in blue or in red, mentioning the Kanjis 'Mihonhin' or 'Mihonban' both meaning sample, and sometimes 'Hibaihin' which means 'product not for sale'. The first ones used to be very simple but the newer ones have more writing on them.
For both 3" Singles which come in a Snap Pack as well as on regular CD cases or Digipacks, the promotional stickers will be placed over the Barcode, sometimes anywhere on the back. These CDs usually do not have a special product number. They have the same number as the commercial product. In the case of a record there is a sticker either on the front or the back. Sometimes it is on the Obi, sometimes on the cover itself.
SECOND, in case of a CD there is some printing on the disc around the whole of the CD. It is either in normal letters or in Katakana saying 'SAMPLE' or Kanji saying 'Hibaihin', product not for sale.
In case of a record there is a sticker on the front or the back of the record and on the label the promotional information is displayed, but the text is rather small.