Information on this page is presented as is. It is presumed to be accurate and safe. I have tried everything listed and have found them to work. Any poblems I ran into are listed, but this does not mean you won't have different problems. Be careful and take your time. Use common sense.
I am not going to talk about how to solder, but rather, ways to improve the cleanliness of your projects. And to do that requires good solder.
For assembling Printed Wiring Boards (or PCBs), I prefere to solder that has organic flux, such as Kester 331. This solder is a little more difficult to make wet, but the ease of cleaning is a huge reward. This flux can be cleaned with regular water. In fact, I generally fill a tub, get a tooth brush (an used one, hopefully) and start scrubing away. I do a final rinse with the water that comes out of my Reverse Osmosis drinking water filter, then blow dry with compressed air. If I don't have compressed air, I will sometimes blot the excess water off with a paper towel.
You do have to be very carefull with Kester 331. It is basically Acid Core Flux, which I am sure you all know you are not supposed to use on electronics. Even if you are not finished with the assembly, when you are done for the day, wash the board in water as described above. Do not leave this stuff sitting any longer than you need to. Overnight is too long. Never do this.
Also, do not mix Kester 331 with any rosin flux. You can use the rosin flux on the same board, but only after you have washed off all of Kester 331. And after you have applied rosin flux, never use 331 flux on that board unless you clean, completely, all of the rosin flux off. Cleaning rosin flux off of a board involves using nasty chemicals. I would just recomend trying to avoid rosin flux on PCB's altogether if you can. If you do accidently mix these two, you will get a big mess. Once 331 and rosin have mixed, it is all but imposible to get this off of the board. Water will not get it off, and neither will nasty chemicals. It seems to be impervious, and the combination is very conductive. Just don't do it.
Another note about Kester 331. Do not use this
flux when assembling cables, unless you can wash it off. One big
problem I have seen is people who use 331 on solder cups, and then slide
heat shrink over the connection. You won't be able to clean it out
and it will start to eat away at the wire.