Using hook-ups?
When I had a 30 amp trailer, I had an adapter that allowed me to plug into 50 amps, and one which allowed me to plug into 15 amps. In addition to the 30 feet of cable built into the trailer, I carried 30 feet of 30A extention cord, and 50 feet of 15 amp extention cord. Plus I invested in a gadget which plugs in and tells you if the outlet is wired correctly, and shows the voltage and frequency (and possibly one other value, but I can't remember for sure).
The adapters came from Camping World (good ones, with a plug on one end, socket on the other, and wire between them, are about $15), as did the voltage meter. The 30 amp extention cord came from either Camping World or WalMart. I don't know where the 15 amp extention cord came from, but I do remember it was a challange to find one with big enough wire (10ga? 12ga? Certainly no smaller)
If you can afford it, I suggest investigating a 'Surge Guard'. Keeps any problems in the power source from affecting your trailer.
Being a disciple of 'overkill', I built an adapter for 20 amps, but never had a chance to use it, so I would not recommend following suit.
For water, it is handy to have an assortment of brass connections (45 degree and 90 degree) and one of those 'flexi-fittings' (4" hose inside of a big spring) to allow you to hook up to any water source, without stressing the hose. I carry 4', 10' and 25' of drinking water certified hose which should be able to handle most hookup situation, along with a 50' flat (canvas) hose on a reel as a small/light solution for long water runs. All my drinking water hoses and fittings have caps on both ends to keep the dirt and bugs out.
Make sure you have a pressure restriction valve somewhere in your hookup to keep the pressure in the RV to 40 PSI or less. I hooked up to my house briefly without one, and blew the water pump pressure sensor and the tube supplying water to the toilet...
I carry a 'manifold' with 4 individual valved hose fittings, in case I ever have to share a water source. I hook up 1 of the 4 with my drinking water, and 1 for my 'sewer' hose (with anti-siphon valve). And 25' feet of 'gray' hose for cleaning the black tank (via backfill valve or toilet wand). Also a good spray nozzle for general cleaning, and the special fitting to fill the fresh water tank. Finally, don't forget a package of spare hose washers.
It is a good idea to have a filter in the line. I use the one from Camping World which claims to filter out bacteria for about $35.