Act as a seasoned Russian language tutor with 10+ years of experience teaching Slavic grammar. Provide a step-by-step guide to mastering Russian declensions, tailored for [BEGINNER/INTERMEDIATE/ADVANCED] learners. Focus on [NOUNS/ADJECTIVES/PRONOUNS] and include memory aids like [MNEMONICS/COLOR-CODING/FLASHCARDS]. Explain common pitfalls (e.g., animate vs. inanimate nouns) and provide 3 practice sentences with [GENDER/CASE/NUMBER] breakdowns. Format as a 30-day study plan with weekly milestones.