Never wind important film directly onto the core. If it does not have a piece of protective leader film already attached to it, either attach a piece of clean good scrap film to it, or wind the scrap film leader onto the core first and then wind on the film proper. Do not attach film to the core by means of adhesive tape. That can cause trouble when the film is wound off again, as it will not readily come off the core and can impose an unwelcome jerk on the newly wound reel. The cores have a slot in their circumference into which the end of the film can be inserted. With practice, even this aid becomes unnecessary.
There should also be protective leader on the outside of every reel. This should be at least sufficient to go twice round a 300 metre reel.
These leaders can also serve the purpose of having written on them whatever identification (such as title, numbers, description, etc.) the archive needs for its records.
There can be conservation problems in using triacetate leaders on films with a nitrate base. In fact, the decomposition of the two bases is very different and putting them in contact can be reciprocally damaging. Using a nitrate or polyester leader would avoid this inconvenience.
Many archives generally use different coloured leaders for the beginning and the end of the film. This quite simple solution allows one to identify them immediately and unequivocally.