>> And about composting, should I wait until I've dug up and made a bed, then compost right before planting? Should I mix it in with the soil or just layer it on top? Composting is very mysterious to me.
The sooner you start composting, the better. Mainly, start collecting stuff to compost. Since you're starting with unimproved soil, it would benefit from having compost mixed in with it (if you can get a shovel or fork or pick between the rocks!)
Since it takes a while for the raw organic stuff to break down into "finished" compost, and you want to garden in the soil THIS summer, you probably don't have time to compost for several months in a pile, THEN mix it with the soil.
So this year, probably sheet composting or a variation like "lasagna gardening" will be more practical. I hope someone will go into more detail, but my understanding is that it's like building a shallow compost heap ON TOP OF bad soil, then growing plants right IN the layer of composting stuff.
I think the only mystery to com posting is "why does everyone have a different method?" The answer is "because EVERY method works well". It's like the movie mantra "if you build it, he will come".
If you pile it, it will compost.
Even the pile is unnecessary - it just makes the breakdown happen faster and hotter. You CAN compost things by making a pile, but during the several months or year it takes junk to break down into black humus, some nutrients and organic matter do leach away. (I do it this way - I like the way finished compost (humus) looks and feels when I add it to an existing bed.)
Or you can just spread raw organic stuff in a sheet on top of the soil ("sheet composting" things like leaves and grass clippings). Even bark and wood will EVENTUALLY compost this way.
Lasagna gardening (please help me here!) is like sheet composting but with a thicker layer of stuff (and maybe it matters more what kind of stuff). You sow seeds or transplant plants INTO the layer of composting stuff, not in the soil under it (I think).
Or you can feed an existing bed by digging holes between plants and burying smelly or unattractive raw stuff, such as kitchen scraps and garbage. ("spot composting"). This way, nothing is wasted. Microbes and worms break down the stuff right next to plant roots and the roots get maximum benefit. (But it feels "ookie" to me, to think of garbage right among my plants' roots.)
Again: start collecting stuff ASAP: leaves, grass clippings, yard trimmings, coffee grounds, kitchen scraps, hay, straw, manure, shredded paper ... almost anything organic . The traditional wisdom is to avoid meat, fat, grease and dairy. I think that is because they attract rodents and dogs. Some people have said "go easy on citrus peels". I don't know about that.
The idea is that soil life like worms and microbes need organic stuff to live. The carbon compounds and N, P and K are their food, and they release more of them than they digest. In the process, they exude other things (humic acids) that help dissolve even more N, P and K out of fine rock grains. Earthworms stir the soil, drive tunnels through it that improve drainage and aeration, and release slime that helps soil grains stick together into "crumbs" or peds that also improve soil structure. Soil fungi also improve soil structure. There are specialized root fungi (mycorrhizae) that form a symbiotic relationship with, and penetrate INTO root hairs. They help extract water and minerals form the soil, and the roots feed them in return.
All these forms of soil life are needed for healthy soil and healthy plants. All you have to do is provide them with food (compost or compost makings), water and air.
"If you build it (healthy soil), they will come."
If you feed the soil life, they will feed your plants.
Soil life can only get their air THROUGH the soil, so it has to be somewhat light and fluffy so excess water can drain OUT, letting the air back IN. Soil needs air spaces, voids, channels, or "crumb structure" A 1905 farming book taught me to call this "ventilated soil".
Stacia and Jewell!
)............ I have planted a couple that I got from friends, not sure what 'color' yet, not big enough to bloom yet and they couldn't remember............ I will only have them in my front yard as they are deadly for my sheep.... The adults pretty much leave them alone....... Lambs? Just like every other 'baby' in the world, everything goes in the mouth ;) ( REALLY want that 'wink'........... sigh................)
Even here in Seattle I felt like I couldn't keep up with that - especially when there is an organic farmer's market every Sunday only a few blocks away 
So I delved very heavily into hardy succulents! Sedums and sempervivums, etc. 
