This the order in which you should try to access papers:

1. Normal Internet search including quotes to force the title and components like “pdf”
2. Organizational/lab pages of the authors. Very many people will put either full papers or preprints on their personal professional pages.
3. Preprint services like arXiv. The ones you look at will be determined by subject area. Preprints will usually only differ from the published work in formatting.
4. Just email the authors. Most of us are so happy that virtually anyone wants to read the paper we spent months on that we will happily send a copy. Because people are busy you might need to hit them up a couple of times, but most will be more than happy to send you a copy, and most publications specifically carve out to allow authors to do that.