How you connect other systems to ServiceNow requires considerable thought. Most of the time, the plumbing is fairly easy, but you need to know where to route the pipes. You don't want to get fresh and waste water mixed up!
At a very high level, there are two points to consider when importing data or creating an integration:
This information should feed into whatever mechanism you eventually use.
In general, if you are exchanging data that represents more than one record at a time, ServiceNow ...