Here is a simple flow chart.
Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.
If you use solar as a battery charger, one rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!
http://w8usa.org/club-library/documents-presentations/
If you full time or use an inverter lots, then populate the entire unshaded area of the roof with panels. I'm considering replacing my awning with solar panels.
For a nice explanation of solar, try this link:
http://www.jackdanmayer.com/rv_electrical_and_solar.htm#The%20Golden%20Rules
