This is the most exciting part of the process because it is the most open ended. I personally have always enjoyed a good dumpster dive. I get the neatest, free-est, most random stuff that I can not live without from the garbage of others. Dumpsters near apartments near the end of the month yield lots of furniture and old stuff people who are moving don't want to take with them so sometimes I will scan my city's apartment/places lots of people who rent units dumpsters at that time and sometimes the yields are epic (*cough* LA-Z-Boy leather recliner and more DVDs and CDs than I care to admit *cough*) Usually the things aren't even actually in the dumpster, and when they are it is usually right on top and easy as cake to get to. I found a semi rust covered smoker, but you could use a grill or old buckets or whatever you think dirt would go in and could have holes preexisting or easily added.
In our neighborhood, we have Big Trash day on the first Monday of the month. A fleet of metal recyclers and swap-meet pickers will roam through the neighborhood scooping up whatever they can use - recycling at its best. I've gotten some good stuff this way and re-homed objects as well.
When you are in the middle of moving, sometimes the stress and lack of time makes people just set out stuff in the hopes that someone will take it. My MIL brought us a carload of stuff just before we moved when I already did not have enough room in the truck. Aaugh!
What bothers me is when they bury good stuff IN the dumpster so it cannot be retrieved.