LINQ to SQL - Am I Hitting The Database?

Like most other developers who have been using LINQ for a while (and in this particular case, LINQ to SQL) - I've unknowingly made a few 'bad queries' that performed great at first, but eventually made some pages crawl. This post isn't necessarily about performance, but if you don't know how to answer that question ("am I hitting the database"), then you'll likely find yourself in a world of problems down the road when you're using LINQ to SQL.