I used my new grass clippers last night and they were rusty! I had used them only one other time. What happened and what should I do to prevent this the next time?
I store my garden tools open so they can dry. Did you store yours closed, if so they may have retained the moisture from the plants you were cutting.

I will spray mine with Silicone spray, then wipe them dry each time before use but I do this to most of my garden tools. If you do this, be sure you wipe them dry to prevent damage to tender plants. I also have a bucket of sand with heavy-duty motor oil poured on top. I plunge the tools into the sand and the motor oil and sand coat the tools. Then I open them and hang them to dry. Here again, I wipe the tools before using to prevent damage to tender plants.