I see from my blog stats that lots of people are looking for soundproofing tips. They come here because I've whined about living in a duplex with wooden floors, holes in the walls, and a barking dog.
I've already explained the importance of stuffing "tundra foam" (or some other foamy substance) into baseboard-cracks, and filling up smaller cracks with "DAP Quik Seal" (or some other sealant). This stops higher-frequency noises (like chatter) and cigarette smoke from drifting in. If you find that your wooden floors have small cracks in them, you might considering putting down a thick rug...I know that the holes from my neighbour's apartment travel underneath my hall and bedroom floors.
But what about the thumps and the barking? I can't block that stuff out of the ENTIRE apartment -- we share a huge common wall that seems to actually TRANSMIT sound -- but I have two techniques for getting to sleep.
First, a box-fan. Get one that's a little bit noisy (but doesn't rattle) and put it outside your bedroom door, in between you and "the noise." If low-frequency bumps are traveling through the floor (as they often do), the fan will not only block atmospheric noise but will also help jam the "floor-signals." If your bed is transmitting those frequencies from the floor and into your mattress, try putting over-stuffed pillows under the bed's legs.
Second, earplugs. If earplugs have never worked for you before, I bet it's because you either didn't buy the right ones or you didn't insert them properly. I'm using "Rexall" foam plugs. I twist them into little cone-shaped corkscrews, pull on the top of my ears (to open the ear canals), push them inside (in the direction of my nose, which seems to work best), then hold the plugs until they untwist and expand. They aren't exactly comfortable -- and hearing your own heartbeat can be disconcerting -- but I've gotten used to them.
And hey, throw out the earplugs when they start to get gross. Fresh ones work the best.