Lots of people talk about writing tests for their code before they start writing their code. This practice is generally known as Test Driven Development or TDD for short. Wh
The benefits part has recently been covered, as for where to start....on a small enterprisey system where there aren't too many unknowns so the risks are low. If you don't already know a testing framework (like NUnit), start by learning that. Otherwise start by writing your first test :)