Almost every Portuguese verb ends in one of three "to" endings — -ar, -er or -ir — stressed on the last syllable. Build the verb straight from the English one; its ending picks the Portuguese one:

• -ar is the default — -ate, -ize, -ify and most of the rest: celebrar, organizar, verificar, visitar
• -er for -end, -ond and -olve: defender, responder, resolver
• -ir for -ide, -mit, -uce and a stressed -FER: decidir, permitir, produzir, preferir