SQL Server Agent Tokens
One of the good things about working with SQL Server is that you are constantly learning. It wasn't until very recently that I learnt about SQL Server Agent tokens. They are like environment variables that can be used within a job step. Books Online states as "Using tokens when you write your job steps gives you the same flexibility that variables provide when you write software programs. After you insert a token in a job step script, SQL Server Agent replaces the token at run time, before the job step is executed by the Transact-SQL subsystem."
For example: I found this very handy for writing job output to a file in the log directory using the SQLLOGDIR token.