How to choose a patent search engine/database for patent search?

There are some free providers which can be used for this purpose.

This is a good start for beginners since it can be used with natural language queries, as we use with the familiar Google Search engine already.

U.S. Patent & Trademark Office (USPTO) keeps organized records of all the published patents by its office. Thus could be a good option if the patent(s) that you are looking for are filed in US. This database is not much intuitive and requires some practice.

The European Patent Office also provides a search engine that includes patents published by most of the European countries and also links to patents from many more countries throughout the world.