The rules of possessives are not complicated, but they still get people all mixed up. For most things, add apostrophe s ('s). For words that end in an s, just add the apostrophe. So you can go to the park and take a goose's picture, or take some geese's pictures. Then notice how that dog's collar is blue but all the other dogs' collars are red. If you still need help, this is the place to find the Answer to all your possessive problems.