- Use blotters; don’t spray anything on your body.
- Clearly mark blotters (do not rely on your memory to recall which perfume is on which blotter).
- Record your first impression on a scale 1-10 on the other side of the blotter (so that you can later test it again without being influenced by an earlier rating).
- Keep all blotters even if you didn’t like some perfumes at first site.
Please feel free to add other sources as comments to the post.