Steve, good question.
A notification will appear at the top of the page as soon as you are the recipient of one, you will receive a PM from a moderator explaining why you received an infraction.
A list of all of your infractions will appear in your User CP (both expired infractions and ones with points still outstanding).
Essentially if you are a recipient of an infraction, you won't miss it

It is quite rare that moderators hand out infractions Steve, despite getting well over 5,000 posts a day, and having over 1/2 a million members we probably average one infraction a day, we entrust our users to be self policing, and the team will typically reach out to people via PM to clarify our guidelines or possibly post in a thread to let someone know that they have violated the rules, it is also distinctly possible on occasions we will ignore some violations.
If our warnings are not heeded, then we typically follow up with issuing infractions on further violations.
You (and 99.9% of our other members) don't have an infraction Steve.