I'm new to growing from seed & keep hearing about waiting for the first set of "true leaves" to appear before fertilizing, etc. My question is, how can you tell the difference between a true leaf and a seed leaf (which, I assume, is what first grows when the seedling first pops up out of the soil)? Maybe it will be completely obvious when I get my first "true leaves", but for now I'm at a loss...
I have no idea why some seedlings do this but many do. You will be able to tell as alot of 'false' leaves usually don't resemble the natural foliage of the plant at all. If you look at the seedlings on this site you will seed quite a few false leaves. If you're unsure wait til the second set appears. http://www.theseedsite.co.uk/db1a.html
The seed leaves are always the first set of leaves to come up out of the soil, for most plants they're very rounded looking and many plants will look almost identical at this stage. Then whatever leaves come after that first set are true leaves. The first few sets of true leaves don't always look like the plant's adult foliage, but they are still considered true leaves. (and the first set of true leaves will be pretty obvious, you won't miss it, but sometimes plants will sit there with just the seed leaves for a little while)
They'll eventually fall off on their own so I'd leave them alone. Anytime you try to pull something off of a fragile seedling there's always a chance of damaging it and there's no harm in leaving them there until they fall of naturally.