To collect leaf litter, all you need to do is grab a few handfuls of fallen leaves (usually including various amounts of soil, dead wood, moss, etc.) and stick it all in a plastic bag. It helps to use some kind of sifter first, to concentrate the litter and avoid filling up the bag with large sticks and leaves, but it's not critical.
After collecting the litter, transfer it to a funnel. You usually want to do this ASAP so that the critters in the litter don't get squished or eaten by the predators you've collected with the prey, but that's not always possible. Keeping the bags in a container with some ice helps to slow the invertebrates' movements and keeps the bags from overheating.
I had a few bags of leaf litter yesterday after a collecting trip, and I decided to showcase how I process the samples by tweeting a series of photos, embedded below. I have access to a room full of dedicated Berlese funnels, but they're easy to set up if you're interested in just testing out the method once.
How to process leaf litter samples: Step 1. Collect leaf litter into a bag. pic.twitter.com/d9w5uzni5x
— Derek Hennen (@derekhennen) September 13, 2013
Processing leaf litter, Step 2: Empty litter into funnel. Don't forget the wire mesh to keep it from falling through! pic.twitter.com/VB6r3Rz5Dj
— Derek Hennen (@derekhennen) September 13, 2013
Processing leaf litter, Step 3: Don't forget to put a cup underneath the funnel to catch the small litter. pic.twitter.com/zNIr7wHNES
— Derek Hennen (@derekhennen) September 13, 2013
Processing leaf litter, Step 4: Replace cup with another cup of ethanol to catch falling critters. pic.twitter.com/d4Y4d8zTEj
— Derek Hennen (@derekhennen) September 13, 2013
Processing leaf litter, Step 5: Empty the previously-caught leaf litter onto the pile. pic.twitter.com/rqv34DEUhT
— Derek Hennen (@derekhennen) September 13, 2013
Processing leaf litter, Step 6: Place light bulb (with or without dome) over the leaf litter. pic.twitter.com/osDpWr5e4y
— Derek Hennen (@derekhennen) September 14, 2013
Processing leaf litter, Step 7: Let funnels for ~3 days. Check for critters. Until then, collapse for the weekend. pic.twitter.com/IqgS7mRygw
— Derek Hennen (@derekhennen) September 13, 2013
In a few days, I can go back to check my samples and figure out what I caught. It's sort of like Christmas morning every time I sort one of the samples: I never know what to expect and it's exciting!