Latin alphabet plus the letter Ñ, representing a voiced, nasal palatal sound. Since Ñ is a separate letter, and not an accented character, it is alphabetized after N. So, in English piñata comes before ping-pong (accented n), but in Spanish it is the other way around (separate letter).
K is not often found in Spanish words, and W still less; they only appear in words taken from other languages.
There are three sounds in the Spanish language which are represented by digraphs, namely ch, ll and rr. Traditionally ch and ll were alphabetized after c and l respectively. In 1994 the Spanish Academy dropped this custom joining other dictionary makers. The reasons for this were because it makes alphabetization too different from other European languages and it was difficult to understand by humans. It also can be noted that it is linguistically incorrect to identify graphss with sounds.
Apart from this, acute accents indicate vocal stress (á, é, í, ó, ú). Also ü is used in syllables güe and güi as a dieresis to indicate that the u is pronounced as [gwe] and [gwi], as it would ordinarily be silent in gue and gui while ge and gi represent different sounds.