Plumbing Layout

Figure out where your prevailing wind is. In the Phoenix area, most of the time the wind blows FROM the East TO the West. Your skimmer should go in the middle on the West side. (Note: When people get multiple skimmers, usually 95% of the debris is picked up by one of the skimmers, so don't waste your time or money on two unless you are building a huge $70,000 swimming "complex".

In general, for most "standard" pool installations you want to use all 2" schedule 40 pipe (Except for things like aerator lines and water leveler lines.( Schedule 40 3/4" for those is fine)). 

Return lines should beset up about 6" from each of the corners of the pool about 2' down from water level, aligned to blow the water straight down each side to create a circular motion.

Which direction should you align the returns to blow the water around your pool? Well the Coriolis Effect would say that you should circulate your water counter clockwise in the Northern hemisphere and clockwise in the Southern. That said, the effect is not much on systems the size of pools, toilets, sinks ... and so, if you have to go counter to that, no big deal. The important part is the placement of returns to circulate the water close to the walls (6", or so, form corners of the pool), and on an upward angle so that fresh water is returned near the surface (Where our faces are) and it displaces the dirty water towards the center of the pool and down where the main drain can suck it in for filtration. (See proper water circulation)  

As far as valves go ... stay away from the cheap PVC valves and brass valves. I Like the 2" "internal dimension" "Never Lube" Jandy Valves best.
You want to have separate 2" schedule 40 lines for the skimmer and the drain. Same with the main return lines.

If you have decided to go with the booster pump Polaris 280 cleaning system, which I recommend(And no, I don't make a dime from recommending them. They are just the best, by far, based on 30 years of experience.), having a 1 1/2" schedule 40 line run to the center of the opposite wall from the skimmer (East Side in Phoenix area) is a good way to go. Otherwise, if you are thinking of installing a suction based cleaner go with the 2" schedule 40. Less risk of plugging the line, better suction transfer to the cleaner ... And yes, if you are going with a suction cleaner, you will need another 2" internal dimension Never Lube Jandy Valve to control that as well.