Our 18 month GSD has just had her second season. Generally, between the 7th-14th day are the days to be extra careful as this is the period when they are accepting of males. The first few days you will notice some pink colored drops on the floor - pretty much like watermelon colored juice drops (pardon the comparison), then the drops will get to brighter red/blood red and at the peak, you will find that the bleeding is more frequent. Occassionally, you might also find 'clumps' of blood. Once you pass this stage, the bleeding will ease off. Be prepared for the smell and this is what attracts males in the neighbourhood to your door. We went through the first one and kept her indoors during the critical period. For the second season, we sent her to the kennel during the critical period. If this is the first time for the GSD, she will naturally clean herself by licking and in the first few days, she will be wondering what's happening to her. Hope this helps.