Choose a good ending
A custom ending (…/spring-sale) tells people where the link goes before they click, which makes them trust it more than a random one.
Keep it short and readable. Brand names of other companies and reserved words are refused, so nobody can make a link that pretends to be someone else.
TipSafe for the people who click
Destinations are checked when a link is created or changed, and checked again as a link gets popular: no other URL shortener, no IP address, no lookalike of a well-known brand.
Add a + at the end of any short link to see where it goes without opening it. Anyone can report an abusive link: it is reviewed and disabled.
Safety