http://masterrussian.com/aa052000a.shtml http://masterrussian.com/aa082100a.shtml

Focus primarily on три склонения (3 declension types), that is, on the three different ways the nouns can change by case. The nouns of the first type will have the endings different from the nouns of the second and so on. For example, the genitive for "собака" and "друг" will be different because "собака" belongs to the first type and "друг" to the second. Try first to get the general picture and only then turn to the cases. Memorizing separately the endings of each case is meaningless, you should know the declension type of the noun to be able to change it properly by case. I hope this link will help you out a little bit: http://www.study-languages-online.com/russian-nouns-declension.html