Tools or Techniques for Removing Grass and Moss from Brick Patio

I just completed a 90 square foot patio. I ended up putting down 4 inches of paver base (crushed concrete), 1 inch of sand, and then the 2 inch patio stones... so I dug down 7 inches all around. To be honest though, I went deeper than that in some places and ended up having to bring in much more paver base (crushed concrete) than I really needed. So maybe I have 6 inches of paver base in some areas. In my opinion, the key was the compacting. I highly recommend you rent a plate compactor. You should be able to rent one for less than $100 for 4 hours and it is completely worth it. You will only use it for 30 minutes but it will make the crushed concrete as solid as rock.

Also one of my neighbors who is a landscaper joked about how far I had dug down... he said I went way too deep and now I can land a helicopter on my new patio. I tend to agree with him that the 4+ inches of paver base was more than needed but still I am happy with how it all turned out.

Couple other notes:

• After compacting the crushed concrete it was smooth and solid. When you walked on it nothing moved... kind of like walking on concrete.
• Lowes/Home Depot sell paver base by the bag but that is much more expensive than having it delivered. 2 tons (approximately 1 cubic yard) of crushed concrete was not enough to cover my 90 square feet to a depth of 4 inches; I probably ended up putting down 3 tons.
• Since the patio was positioned next to a concrete sidewalk, I used an 8' 2x4 with a piece of scrap wood nailed to one end which gave me a depth of 3 inches (the sand and paver depth). Then I pulled the 2x4 back and forth across the area (with another person holding one end on the sidewalk) to level out the paver base before compacting (and to know where the shallow/deep spots were).
• I used 1 inch diameter pipes to give me the 1-inch depth for the leveling sand. Put two pipes down on the compacted paver base parallel to each other and then pour the sand on top. Then pull a 2x4 over the pipes to level the sand. Remove the pipes and then fill in the indentation by hand. Now lay your pavers (or patio stones).
• I used polymeric sand to fill the cracks in between the individual patio stones.

Updated with photo for @Chris Marasti-Georg (2013-05-20):

(1) Is this even advisable, or should I just extend the concrete out to the entire area I want for the patio before laying stone (adding considerable cost)?

Rolls-Royce job (Money no object): Extend the concrete slab out to the area you wish to pave or remove the existing slab and start allover again.

(2) Assuming I don't extend the concrete, what should I do when the stone transitions from the concrete subsurface to the dirt? I'm nervous that cracks will occur over time, and I'd like to do whatever I can to avoid that.

Good enough job (and what most paving pro's would do, at least the ones I know back in the UK): Excavate 6 to 8 inches (150 to 200mm) from the area you want to extend into. Back fill that area with sub-base (crushed rock) material. Back fill in 2 to 3 inch (50 to 75mm) layers, each layer should be "properly" compacted. This will give you a sub-base that is "nearly" as good/stable as the existing concrete slab.

• Something to consider, regardless of chosen method, how is the paving area going to drain? Do you need to put in some sort of drainage system , thus preventing the surrounding softscape from flooding due to the new hardscape?