There is nothing quite as annoying than finding a wet spot somewhere in your home and discovering that a pipe is leaking. There are all types of pipe leaks as some can flood your home while others only drip. The approach to use when stopping a leaky pipe is to determine where the leak is located. If the leak is at a joint, tighten the joint but it is is in the pipe itself, you might have to remove that section of pipe so that it can be replaced with a new section.
If the pipe is made of copper the new section will need to be soldered into place. If you do not have a soldering tool or the necessary skills to do this then you could use the old pipe patch trick. All hardware stores sell these kits or you could simply make your own using a piece of rubber from an old inner tube and a C-clamp. The kits sold in stores contain a rubber pad that cover the hole and then you place metal plates on the rubber and then screw them in place. Believe it or not, these patch kits can be a permanent solution if the pipe is in good shape otherwise.
You also could buy some waterproof tape and wrap it around the pipe. There are also self-tapping plugs for sale that do a nice job of stopping a leak. Many homeowners opt for the waterproof tape because it is inexpensive and very simple to put on. Just be doubly sure that the pipe is completely dry otherwise the tape will not stop the leak.
If the leak is so severe that it has flooded your home, you might want to call in a plumber. If you were to fix the leaky pipe yourself you may end up with another flood soon because the chances are good that the pipe will be bad in other spots as well. It is better to be safe than sorry when it comes to having your home flooded and the money you spend on a plumber is nothing compared to what you would have to pay to have your home pumped out.
On a final note, just because you find water puddles or drips from pipes in your house, it does not always mean that you have a leaky pipe. It could be caused by sweating pipes so check to see if it is indeed condensation. If so, simply buy some pipe insulation and wrap it around the pipes in question.