Soil - you will figure out, you have many great suggestions here!
I've started with the raised beds too, due to not owning a tiller, and my soil is a very hard, dense clay. Size - almost as yours, 2x4x10 (two of those, and two 2x3x4)
rainbowgardener wrote:...jal_UT may know better than me, but once you have the 2 tomato plants and 2-3 pepper plants and onions in that one 4x8 bed, it's still hard for me to imagine where the cucumbers are going to go...
Here is an example of one of the beds, and what was in it (now - asleep for the winter):
1. Black Krim Tomato
2. Cherokee Purple Tomato
3. Red Bell Pepper
4. Cherokee Purple Tomato
5. Brandywine Sudduth Tomato
6. Yellow Bell Pepper
7. Valencia Orange Tomato
8. Yellow Boy Tomato
9. 10, 11. Boston Pickling Cucumber
12, 13, 14, 15. Red Leaf Lettuce
16, 17, 18, 19. Red Onions
20, 21, 22, 23. Radishes (Champion, Icicle)
24, 25. Eggplants Ichiban
1 plant of Sweet Basil under each tomato plant too
My soil ended up being very very loose, and allowed tomato, eggplants and pepper roots to travel throughout the bed, while onions (4 per square) didn't need much, radishes 16 per square felt like very much at home, and red leaf lettuce with 4 and 3 alternating per square did not mind at all the "space sharing"
Cukes - the netted trellis provided plenty of support for them, and allowed me to direct the three vines where they needed to go, up, and over to the other side with no interruption for anything else. And the great part about the trellis - frame from 1/2" conduit poles $1.60 for 10' pieces, $10 for entire trellis - you can expend the trellis for cukes beyond the bed at any time for next to nothing!
Here is a snap of the early season, just a week or so after planting:
Maybe my plan was a little aggressive, but it worked, I fed plants biweekly with fish emulsion, small amounts of liquid bone meal every 4 weeks and kelp every other 2 weeks (mostly foliar spray).
Play with your garden, experiment and enjoy it!