If u followed my 'Ible on "How to Disassemble a Pallet", u may still want to get the nails out. I know that some of you rejected that disassembly method out of hand because of the desire for nail-free wood. Have no fear. Nail-Free Slats are EASY! Nail-free 2x4s are a pain but doable.

Step 1: Denailing Slats

Turn the slat upside down so the heads of the nails face the dirt. Some nails will simply fall out w this change in orientation.
Grab a blunt, waste nail & a claw hammer.
Place the blunt tip of your nail at the cut end of the nail in the board. Tap firmly but gently.
Once the board nail is out ~1/2 way, go to the next nail.
After all nails in that line are out half way, flip board over.
Using the claw portion or another clawed tool, pull the nails all the way out.
Repeat for the next row of nails.

EAZY PEAZY!

Step 2: Denailing 2x4s: Begin

These are bit trickier. I usually just use them w the nails in them, so that's not an issue. However, certain tools (like a Router) have negative issues when dealing w nails so before I use those tools I have to denail it.

Step #1
I have 2 methods for removing the nails from the 2x4s depending on what I'm going to do next.

Method #1
If I'm going to router the center out anyway, I usually use a circular saw to cut a line 3/4"-1" deep down the middle of the 2x4 removing the wood from one side of the nail. Get as close to the nail as possible without cutting the nail. This is great since I can do multiple nails simultaneously & get the boys to help w the next 2 steps.

Method #2
If you're only trying to take out 1 nail or keep the wood as unmarked as possible, use your drill & a 1/8" bit to drill a hole next to the nail to be removed. Again, the idea is to remove the wood next to the nail.

Step 3: Denailing 2x4s: Finish

Step #2
Using a hammer & an old nail, nail the nail into the board opposite the hole u just drilled or the saw cut. The nail is holding to the wood. You're giving it force to the SIDE to let go of the wood & fall into an area so u can grab it w less resistance to pulling out.

Step #3
Using old, dull, pointy wire cutting pliers, grab the nail in the jaws, squeeze, & level up. U may need to grab again, put a small block under to get leverage, grab lower, squeeze tighter, etc. Basically, if u can get your pliers around it & the nail is move from its original hole, it should come out.

Step 4: Conclusion

Like I said, a pain but doable. Most people merely need to denail the slats. I like the look of the old, rusty nails in my rustic projects, so I tend to work around them. But, sometimes even I need to. So I hope this helps.