I've done it.
It is simple in practice, difficult in theory.
First, you need to size your pipes. A 1/2 inch pipe is great for supplying 1 washer, 1 sink, etc. For more than 1 point of use, you must use 3/4 inch pipe. It's ok to split the 3/4 and have 1/2 inch going to each individual connection. I would recommend running a main line in 3/4 and then using Ts with 1/2 inch lines to each individual connection.
As for actually soldering, I was taught in 1 hour by a pro.
First, you will need a torch. Cheap torches have a gas valve you turn and then you must light it with a striker. Better torches have a button you press that, in a single action, opens the gas flow and strikes a spark. All you need to do is push the button and it lights itself. You can either lock the gas on or hold down the button. This automatic torch is a godsend. I would strongly recommend you get one for both convenience and safety. IT IS WORTH EVERY PENNY!!!
Second, you will need gas. Propane comes in blue bottles and is pretty forgiving because it has the coolest burn. It is also the slowest, but that is an advantage if you're just learning. MAPP gas comes in a yellow bottle. It burns hotter than propane and will allow you to work faster but it is less forgiving. I recommend you stick with the propane. You will need MAPP gas, however, if you are soldering pipe larger than 3/4 (not likely in a home).
Third. What parts to use? You will need pipes, pipe joints, and valves. Buy ONLY ball valves. Older style gate valves are cheaper, but you have to dismantle them so you don't melt the guts with the torch. Ball valves can take the heat and they go from shut to full-on in 1/4 turn. Valves take a long time to heat, but be patient.
Fourth, you will need tools. The torch is covered above, but you will also need a pipe brush, flux, pipe cutter, and solder. Buy a good all-in-one pipe brush. It has a wire brush on each end for cleaning the inside of the fittings and valves, a 1/2 inch on one end and a 3/4 on the other. It also has 2 holes in the body with wire brushes. These are for cleaning the outside of the pipes, one hole is for 1/2 inch, and the other is for 3/4. You make the pipe and fittings all nice and shiny before you flux and solder. If you don't make the connection clean, it won't seal. When in doubt of whether it is clean enough, keep brushing. You can also use sandpaper in lieu of a wire brush, but the brush is much easier.
Flux is essential. Buy lead-free plumbing flux and use it. You don't need as much flux as you might expect, but being new, I would recommend using lots of it. Not everyone fluxes both the pipe and the connector, but I do and I recommend you do too. The flux helps draw the molten solder into the joint and ensures a solid connection.
Solder is what gets the job done. Standards for solder have changed over the last 20 years to eliminate lead content. If you have old solder, don't use it, get the new stuff. The new stuff melts at a higher temp than the old stuff, but better to be safe. Make sure you buy plumbing solder and not electrical solder. You may want to try some flux core plumbing solder too. It might be a little more forgiving.
The pipe cutter is important. Buy the longest length of copper you can because it's cheaper per foot that way. If you need to have the pipe cut to fit in your vehicle, that's ok and the folks at Lowe's or Home Depot will do it for you. Just tell the person at the register the pipe was originally 1 piece. Your cutter will consist of a small tool which fits around the pipe and has an adjustable handle. Tighten the handle until the tool's cutting wheel touches the pipe and spin the tool around the pipe. Tighten the handle every few revolutions and repeat until the pipe is cut. Do not over tighten the handle or else you will dent the pipe and it won't fit into the fittings or valves.
Fourth. Technique. I suggest you get some spare pipe and fittings and practice for awhile before you actually start plumbing. Cut some lengths of pipe then clean the ends, clean the fittings too. Then flux some of the ends and fittings and put them together. Do one joint at a time and then more as you get a better feel for it.
Unwind some solder from the roll and roll it around the pipe. That is about the right amount of solder to use for each joint on that size of pipe. Next, unwind more solder from the roll so you can hold it without the heat coming back up the solder and burning your fingers. Finally, bend or straighten the solder as you deem fit so you can hold the solder with 1 hand and the lit torch with the other.
Light the torch and apply the heat where you want the solder to go, do not heat the solder directly. Don't heat the outside edge of the joint either, heat the back side of the joint so the solder flows in that direction. The joint is hot enough when you touch the tip of the solder to the hot joint and it melts by the heat of the copper and flows into the joint. You don't really need to move the solder around, that's what the flux does. When the molten solder runs out of the joint you have used just a little too much, but not enough to be a problem. If the copper starts to discolor a lot, you have overheated the pipe and likely burned off the flux. When this happens, you must take it apart, clean it till it shines, flux, and solder again.
Fifth. Some cautions and tips.
Copper conducts heat very well. The pipe will get hot pretty far from the joint. To stop the spread of heat, wrap the pipe with a wet rag, just not too close to the joint you are trying to solder. You may use a wet rag to quickly cool a hot pipe or joint. If you are soldering near wood, spray the wood with water before you solder. Also, keep a squirt bottle handy in case something does start to burn. Soldering a joint is not slow so if something starts to smolder, keep soldering until the joint is done, you can spray the smoldering spot long before it becomes a hazard.
If you are soldering a joint, solder both ends of the joint at the same time. Heat the joint, apply solder, then heat the other side very briefly and apply solder there too. This way you won't melt one joint while you solder the next one.
After you have soldered a joint or set of joints, cool the hot pipe with a wet rag and wrap the pipe with the wet rag so you don't melt your new work when you work on the next joint down. When soldering the connection to your existing plumbing, wrap a wet rag around the pipe so you don't melt any joints in your existing plumbing.
Always solder dry pipes because steam will find a way out through molten solder and result in a gap in the solder joint. Always solder ball valves with the valve open to allow any steam to escape. Also, when you turn on the water, the ball valve's handle may leak a little. There is a nut that holds the handle on and another behind the handle, make sure these are tight.
When buying straight joints, always make sure to get ones that have a small indentation that serves as a pipe stop. This way, when you insert the pipe, it stops at the right spot and there is enough joint left for the other pipe.
Get a washing machine connection valve so you can use a washing machine hose to connect your practice plumbing to a hose spigot to pressure test it before you tear loose on your house. It is not recommended to reuse previously soldered joints and valves, but cutting the pipe to which the valve is connected and connecting that to your new work is just fine, just so long as you don't accidentally melt the valve's joint.
You may want to consider an anti-hammering device. This is essentially a vertically-mounted section of pipe which connects to the plumbing at the bottom and a cap at the top. This traps air in the vertical pipe which acts as a shock absorber. If the washer shuts off the water, the air will compress so the pipes won't hammer.
Be patient, take your time, and make sure there is someone else nearby to serve as a second set of eyes. You will be playing with fire.
Clear as mud?
Dave
PS: If you have doubts, get someone to teach you. Maybe there's a small class at a local community college or vocational school.
