COMPER
A competition-entrant
 
COMPING
entering competitions

LWE:
The LONG WHITE ENVELOPE! This is how the prize notification letter usually arrives.

Qualifier:
This is the item purchased to allow an entry where a purchase must be made.

Proof-of-purchase/POP:
Usually the till receipt, label, or piece of the qualifier wrapper, that shows a purchase has been made.

EF:
An entry form.
These are a loose leaflet (usually displayed in a rack near the promotional product); on-pack (e.g. cereals); printed in newspapers/magazines' small labels stuck-on promotional packs (bacon/cheese etc.); or bottle neck collars