Links are usually created by automation rather than by hand, but a few things are worth knowing before you rely on them.
Duplicates are prevented automatically
Creating a link that already exists returns the existing one rather than adding a second, so automation that runs more than once does not produce a pile of duplicates. Note that the link type is part of that check — linking the same two records as both "related" and "duplicate" creates two links, which is intended.
Agree a vocabulary and stick to it
The link type is free text. That is flexible, and easy to make a mess of — "duplicate", "duplicate-of" and "Duplicate" are three different types as far as ActiveManage is concerned, and they will not group together in a report.
Decide your list of link types before you start using them, write it down, and configure your automation to use exactly those.
Direction
Every link has a direction — a "from" record and a "to" record. For a symmetric relationship such as "related" it does not matter. For an asymmetric one such as "caused by" it is the whole meaning, so make sure your automation creates them the right way round.
Links do not carry permissions
A link is only a pointer. It does not grant anybody access to the record at the other end, and it can point at a record the person looking is not entitled to see. If you display links in your application, apply your normal permission checks when resolving them.