1. Introduction

2. The role of PN as astrophysical tools: why we search for them

3. Current PN catalogues & past problems

4. PN discoveries and characteristics at non-optical wavelengths

5. The problem of contaminants and their effective elimination

6. Reliable distances to Galactic PN

7. The era of high quality, multi-wavelength imaging surveys: a golden age of PN discovery and catalogue purity

8. The Future