(Small) Things that could make your graduate life much easier.
Note: Here you will find only simple things each of which could be learned within a short time period (a week perhaps). There are however other more important things as well, which tend to take major effort. For example, English is very very useful, but takes years of effort. Thorough understanding of core subjects --- absolutely essential, but takes years. Even learning some typical programming languages such as C++/Java can take many weeks or even months. They should be discussed separately.
Computer and Programming
Linux/Unix: frequently used commands, shell programming
Script Languages: Python/Perl
Regular Expression: useful and common for diverse things including editors, system commands (e.g., grep/sed/awk), script languages, etc.