Hello Fleur. I would like to complement the previous answer. If you and your friend are close, your can also end your informal letter with good wishes like: "Nos vemos pronto!" (See you soon!) "Saludos a tu familia" (Greetings to your family) "Que tengas un buen viaje" (Enjoy your trip) "Un fuerte abrazo" (Hugs - strong hug) And then your name, to complete the structure of the letter: Nos vemos pronto! Atentamente, Fleur

Hello, if they are your friends but you don't know them very well then you can use a typical expression for this kind of situations: ---- Agradeciendoles por su atención a la presente reciban un gran saludo. Abrazos Fleur Holland --- This is not very informal neither very formal.

Find a sample letter and imitate. You just need to replace names. http://spanish.speak7.com/spanish_letter_samples.htm