If you are unfortunate enough to find a broken or cracked window in your home, you'll need to get it repaired quickly. Windows can crack or break for various reasons. A line-drive from the neighbor kid's baseball bat, being struck by a tree branch or other storm debris, a rock thrown when run over from a lawnmower, the house settling, or even improper window installation can all cause window glass problems.
If the repairman can't get to your house right away, you'll need to do your own emergency window repair as a temporary fix to keep the elements out of your home and to maintain the temperature inside your home. The type and location of the window glass damage will determine what your temporary fix should be.
For a window crack, your main objective is to keep the cold air and rain out until the pane can be replaced. Using duct tape or clear heavy packing tape, apply it on top of the crack on both the inside and outside of the window. Be careful not to push too hard or you may end up making the crack worse or breaking the pane out of the window completely.
If the window is shattered or has a gaping hole, you'll need to remove all of the remaining glass pieces from the window. If the pane is very large, you may need to first remove the window frame and place it on a flat surface before removing the broken glass pieces. But for most window sizes, you should be able to accomplish the task with the window frame in place.
First, be sure to wear heavy gloves and protective eye wear. Lay down a tarp to protect the area around the window as well as to collect any pieces of glass. You can remove the broken shards piece by piece, which is often easy to do. Or you could cover the broken window pane completely with masking tape, then gently tap the glass with a hammer handle to loosen it.
Now you need to cover the open area until the glass can be replaced. You can cover the area with thick plastic or a section of heavy duty trash bag, stapled or taped over the opening. If the window is a double pane window but only one pane was broken, this will give you some additional protection. In cold weather, you can create a bit of a thermal barrier by adding bubble wrap or hanging a heavy quilt over the entire window.
For extensive window damage, you may want to consider boarding up the entire window opening. It's safest to enlist the help of a friend or family member since this is much easier with two people. You'll want to drill plywood into wood studs, so locate those on each side and under the window. Measure the window opening and cut a sheet of 1/2" plywood to size adding at least one inch beyond the location of the wood studs. Attach plywood using screws that will go into the frame by at least two inches, and attach screws every 16 inches.
A final note: prior to any window DIY repair, it's a good idea to take photographs of the window damage before and after your temporary repair in the event that you submit a claim to your homeowner's insurance.