The best way to start depend on the person who is starting.
If a person is an artist who for ex. has some digital artworks they can go to some of the NFT marketplaces and look at the documents on the specifics of the marketplace does deal with NFT.
If a person is a developer they can get a template of the ERC721 or alike NFT smart contracts, deploy it on one of the testnets using for ex. Remix and test functionality.
If a person is a marketer or a collector/holder to be of NFTs they can read the many NFT related articles on Medium.com and Hackernoon.com .