Hey! I can be relevant in this forum!
Pipe slope: yes 1/4" per foot (2%) is my usual target, but 1/8" per foot (1%) can be done.
Cover over system components: 1-3 feet is the goal. 1-foot for protection of the tanks, etc. 3-foot to keep oxygen in the system for the break down of ammonia. In simple terms, there are two important bug types in septic systems; aerobic organisms (breathe oxygen) and anaerobic organisms (don't breath oxygen). Each type of bug does its own thing best, so you need both to fully break down effluent, too deep and you lose the first step of the nitrogen process.
Pumping effluent: There are many packaged systems available, Myers puts out a decent one, e-one puts out an expensive one (but this is a tank that will last and last). These units come fully set up to go, basins, control panels, alarms and all. There are two types of pumping. The first is pressure dosing which involves squirting the effluent evenly across a leaching area with pressure (this takes considerable design). The other involves gravity dosing which is simply lifting the effluent higher to a d-box where it flows into the leaching area by gravity. If you pump to a leaching area, put a tee or splash plate on the d-box and check that you don't overdose the d-box before you bury it, it is common that you need to seal the cover. Remember that every time that pump turns on, it uses energy so avoid pumping whenever you can.
If you have a well and septic on the same lot, or if you are near surface water or wetlands, or if groundwater is close to the surface, do us all a favor and install an effluent tee filter on your septic tank. They aren't too expensive, and with regular (easy) maintenance they really help break down effluent. Zabel is one source: (they also sell a bunch of cool septic components and pump systems)http://www.zabelzone.com/wastewaterfilters.htm
I cringe when I hear about areas that don't have decent septic regulations and allow any Joe with a shovel to install some pipe in a trench and call it a leaching area (this isn't to say that nobody but engineers or installers can do this work, but someone with some valid experience should be doing the work). It is sooooo easy to destroy our drinking water supply with inadequate sewage treatment. Nitrogen is quite nasty and can even be fatal in babies.
Our State regulates septic systems and provides some decent rules:
*100-foot separation from drinking water wells to leaching area (effluent plumes can easily go 50 feet or more from a leaching area given the right circumstances)
*4 foot separation from the bottom of leaching areas to seasonal high groundwater (5-foot in rapid percolation areas) to provide enough time for effluent breakdown prior to reaching the groundwater
*50-feet leaching area to wetland setback (let's keep those critter habitats clean)
I'll get off my soapbox now, I hope I got this stuff in understandable terms (us engineers sometimes talk funny, BOD, TkN, TSS and whatnot). If you want a decent set of rules to follow check out our state regulations: http://www.mass.gov/dep/brp/files/310cmr15.pdf
These are very strict, but we have seen improvements in water quality since implementation of these regulations.
Remember: I only play an engineer at work so take this all as opinion only