Welcome to the forum and good luck with your plans to visit and eventually move here, it's a great country to live in.
My advice is to have a good think about how you want your life to be here - do you want to live a quiet life in a tranquil rural location? Live in a city? something in between? Do you want to have other expats to mix with or immerse yourself into Portuguese life? Do you want to live in a holiday resort location or in a normal working city/town/village? Do you want easy access to cultural events? find out where they happen! Do you want to be close to an airport? travel links? Will you have a car? Do you want to be near the sea or countryside or both? Do you want a big house with lots of land or an apartment in the centre of a town? What is your life like now? What elements of it do you like/want to keep?
I think the more you question yourself about the type of place you want to live in, the easier it will be to narrow down your search once you get here (or to ask better informed question on this forum). Life in the countryside here is very different to life in the city, until you get to know the country well you can miss out on visiting places that could be perfect for you! If you're lucky you will visit and find somewhere that just feels right for you, but research will help you to find it. Good luck!