We all know that Grammer can be a difficult thing to master, and even the masters make mistakes. There are so many rules for many different things, and for a new writer it can often be overwhelming. Common errors lie with the difference between effect and affect, or lose and loose.

Unfortunately there is no quick way to learn these. Most of us know this through years of slaving away with quill and scroll (or keyboard and screen), and even when you're at a point in your writing career when you're happy and confident that you know enough to get by, something will always come up and bite you on the bum.
This happened to me yesterday. One of my critique buddies pointed out that I had used passed instead of past. Reflecting back on my work, I was under the impression that the option I used was correct. Now I'm truly confused.
So I'm calling upon all my writing buddies out there for help. Tell me, is there an easy rule that you use when it comes to past or passed so that you know the one you write is correct? Has there been a time when you've had to stop and think which is which, and then remembered a little rhyme that maybe you were taught at school or that you come up with yourself to tell you???
How do YOU know which one to use...?