Where to Renew Passport: passport unity of government in your home country or overseas embassy or consulate.
How to Renew Passport: finish the renew application form (online form or printed form) → prepare passport photo or take a photo on site → get ready your most recent passport if requires → prepare other related documents, like name change certification, etc → find the nearest acceptance facility or regional agency → make an online appointment → visit the office, submit all required materials in person → pay passport renewal fee → wait and collect your new passport.
When passport holders apply for the passport renewal, the old passport is required to surrender for invalidation. While in some circumstances, the expired passport is not required to be surrendered or invalidated, if it contains an unexpired visa, for instance.
The passport renewal in some countries has some specific rules of age and length of expired date, like America. The U.S. citizens with the age of 16+, have a valid passport in their possession, can enjoy the right to renew their passport. However, if your passport has expired more than 15 years ago, damaged, lost or stolen, issued in previous name, you need to apply a New Passport Application in person.
Warm Tips: Renew your passport several months before the it expires. Check the expiration date because some countries requires certain remaining validity, like at least 6 months is needed for applying a China Visa.