Tiling onto plasterboard whats the best thing to do

If it’s in a bathroom I’d personally use moisture board/ green plasterboard and tile directly onto it no additional work is required.

Use SBR primer, scrim tape joins and tile away. If it's a wet area such as a shower enclosure make sure you use a tanking system to waterproof the plasterboard.

If newly installed plasterboard you should be fine to tile directly onto it some people like to have it skimmed prior but I've seen many trades tile directly onto the board.

Need to weatherproof in bathroom area and pva in the other suprafaces