Si es una carta formal, puede poner "Atentamente", "Se despide atentamente", "Muy atentamente" "Reciba un cordial saludo"... Si es una carta para familiares, amigos etc..."Recuerdos", "Un abrazo", "Saludos", "Besos"...

After the signature usually nothing, before the signature, it depends: Sinceramente ---> Sincerely (formal/business letters) Atentamente ---> Attentively (formal/business letters) Amistosamente ---> Friendly (informal, rarely used) Saludos ---> Greetings (Friendly, formal and informal) Muchos saludos --> A lot of greetings (Friendly, formal and informal) Abrazos/Un abrazo ---> Hugs (Informal, very friendly, usually for people you know, friends, family, etc.) Besos ---> Kisses (obvious)