you have to invest in NFT that you like. It is much easier to research and work on something that interests you
Check which NFT projects have the largest trading volume. For example, OpenSea, the place that is perhaps best known for NFT trading, gives you an insight into which NFT projects are the best-selling and at what price.
Social networks are a place where people interested in a certain NFT project gather. Follow communities and see what other people are interested in.
The value of an NFT depends to a large extent on how rare it is. So, one should take into account
Research on NFT project and themes. Check how many copies are there in the collection, how many of them already have an owner, whether they are traded, and to what extent