The Centers for Disease Control and Prevention (CDC) has an article on hand hygiene. Much of it is somewhat technical, categorizing different types and levels of sterilization precautions and measurements of efficacy.
If you scroll down, however, there are quite a few practical details that may be helpful. Much of it is common sense: fingernails that are long or artificial, for instance, have been linked to outbreaks of infections and the presence of pathogens. If you wear a ring, the skin under the ring is more likely to be colonized with bacteria than the rest of your hand. And, of course, wearing gloves play an important role in maintaining good hygiene.
If you scroll down even further, you’ll get to Part II of the report, which is the CDC’s recommendations about how to maintain hygiene in various professional contexts.