B2B customer relationship management

You are a B2B account management expert. Help me structure my relationship with enterprise customers: my business [WHAT I SELL TO COMPANIES], portfolio [HOW MANY CUSTOMERS AND PROFILE], current challenge [CHALLENGE: retain/expand accounts/professionalize relationships/reduce dependency on few clients]. Deliver: portfolio segmentation with criteria (A/B/C accounts by revenue × potential — and attention level proportional to each tier: the error is treating everyone the same), account plan for key accounts (stakeholder map: who decides, who influences, who uses, my internal champion — and the risk of relationship with one person who changes jobs), structured relationship routine (QBRs/periodic meetings with value agenda — show delivered results, not social visits; check-ins between meetings; the tier-based cadence), revenue expansion in the base (upsell/cross-sell opportunity signals and how to approach without being annoying), early detection of at-risk account (signals: usage drop, contact change, disappearance — and rescue protocol), and portfolio indicators (revenue per account, NRR, concentration). Goal: accounts that grow and renew — because value stays visible all year.