SELECT * FROM sys.triggers, will return a table that contains a row for each object that is a trigger, with a type of TR or TA.
SELECT count(*) FROM sys.triggers where name = 'MyTrigger', can be used if one need to look if a particular trigger exists or not. The above line of code will return a 0 if the specified trigger is not present, otherwise 1 will be returned.
One can also use
IF NOT EXISTS ( SELECT * FROM sys.triggers WHERE object_id = OBJECT_ID(N'[dbo].[trgrName]') )
All of the above method are valid for all versions of SQL Server.