This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Test For Exposure. When opening a package of paper, avoid exposing it to bright light (as previously suggested). If uncertain which side has the sensitized surface, determine which side of the paper shows a tendency to appear concave. This will be the sensitive surface, as the paper curls slightly toward the coated side. When ready to make the first exposure, cut a sheet of paper into small strips, about one inch wide. Place one of the strips over an important part of the negative and make an exposure, using your best judgment as to the distance from the light, and time of exposure. Develop the print and if it is not satisfactory try another strip, varying the time or distance as indicated by the first trial. When the best possible results are secured from the negative in question, proceed to make the desired number of prints from the same negative, giving the same exposure. If time and distance are identical all the prints should be equally good. By comparing other negatives with the one printed from, you will be able to make a fairly accurate estimate of the exposure necessary for each. If care is exercised good results should surely follow in every case.