On the last live blog you were making comments about beginner guide blogs to get views. I would think that you could do quite well with these. I would ask for one on cost effective design.
May your wish be partly to mostly granted.
I figure your intent is to hear from Dave, but I'll throw in my two nH about the remainder. I'm a noob still, but it is a forum after all!
What are the major costs in an electronic design, (pcb, components, manufacturing where should one be looking to make sure you will have a quality cost effective part)
In my limited experience, from a one-off to low production hobbyist perspective, most of the cost is in UI and enclosure. Take the typical guitar pedal or amplifier as an example. The pots, jacks, switches, and case make up the vast majority of the cost. This assumes a good deal though, for example, that you're doing the boards yourself and not including start up costs. The electronic parts themselves tend to be the cheapest budget category, though it depends on what you're doing. This is mostly from my limited analog perspective, but I definitely understand why most kit manufacturers sell just a board, or a board plus parts.
Should you aim for a single sided design or 2 sided, (should all the parts be on one side of the board? what is a valid reason to make a 2 sided board?) 2 layer or 4 layer board with closer packed components, ( what is a valid reason to step up to a 4 layer board)
I think these decisions revolve mainly around noise performance, intended size, and ease of manufacture. Low level or high speed signals will require attention to grounding (see other related threads) that's much more easily accomplished with multilayer boards. If you need to fit a particular space, and it's small, multiple layers will help you pack things in tightly, which also helps with noise. If you're etching your own boards you're obviously limited in your options. I've read that keeping components on one side of a two sided board makes automated manufacture much easier.
Jelly bean parts to include in your design or why not to use jelly bean parts, (a list of good jelly bean parts)
There's been a few good threads on jellybean parts with at least one list, a quick search should turn up a few. We should really get a sticky going.
Things to include for trouble shooting the design, Test ports/headers for probing the circuit, (or other things that a new person might overlook)
Good call on this one, it's hard to think of everything.
Sorry if this seems a bit cut short, I've got to go at the moment, someone's stopped to visit.