The three axes
Coast, mountains, city or countryside. This is the biggest single filter. Be honest about the gap between a holiday and a life: a beach resort that thrills you in August can feel hollow in January, while the mountain village with the stunning view is a long drive from a supermarket. There's no wrong answer, only an honest one.
Traditional Spain or an international community. A quiet inland town gives you immersion and authenticity, and asks you to function in Spanish. The established expat areas of the south-east coast and the islands give you an easier landing, English-speaking neighbours and a ready social scene. Many people want a bit of both, which itself points to certain places.
Connected or remote. How close do you need to be to an airport, a hospital, a train line? If family will visit often, or you'll fly home regularly, proximity to an airport with the right routes quietly becomes one of your most important filters.
Answer those three and you've gone from "Spain" to "the inland towns of Andalucía within an hour of Málaga airport," which is a search you can actually do.