Depending on what debts appear on your report, your approach changes. Collections accounts, charge-offs, and unpaid debts all affect your score differently.
Old collections and charge-offs: Don't pay these immediately. Once you pay, the account becomes "active" and restarts the 7-year clock in some cases. The older the debt, the less damage it does (a 5-year-old collection hurts less than a 2-year-old one). Focus on building new positive credit first. After 2-3 years of perfect credit building, consider negotiating settlements when you have savings.
If a collector calls, respond professionally in writing. Say: "I request validation of this debt under FDCPA requirements." They have 30 days to prove the debt is legitimate. Many can't, and the debt gets removed. Send this by certified mail to create a paper trail.
Active debts: If you have accounts still in your name (medical debt, utility arrears), prioritize paying these. They're current threats to your score. Call the provider, explain your situation, and ask about payment plans. Many utility companies and hospitals offer hardship programs for people rebuilding after incarceration.
Negotiation power: Once your score reaches 580-620 (doable in 12-18 months), you can negotiate from strength. Contact old creditors and collectors with a written offer: "I'll pay 40-60% of this debt in full settlement, paid this month, if you remove it from my report." Get any settlement agreement in writing before paying anything. This is called a "pay for delete."
Default reporting: Some accounts show as "unpaid default." These fall off after 7 years automatically. Don't pay these old debts unless you need a specific loan (mortgage, auto loan). Paying old defaulted accounts sometimes hurts your score temporarily (refreshes negative item on your report).
Your priority order: 1) Current obligations, 2) Secured card + credit builder (new positive history), 3) Negotiate old debts after 18+ months of perfect credit, 4) Don't pay very old debts unless absolutely necessary.