This depends on personal habits or the amount of money spent.
If you have more money, use a professional patent search database, such as Derwent Patent Database.
I personally use it for free (I am a poor person~~~).
For domestic patent searches, I generally use the SOOPAT website or the official website of the State Intellectual Property Office.
Foreign ones are more commonly used on the European Patent Office website. In special cases, search on the website of the patent office of the country where the patent is located.
PS: You can find the websites of foreign patent offices and patent organizations on the official website of the State Intellectual Property Office in the "Homepage> Document Services> Internet Patent Search System".