Good article on the definite articles "el"."la" "los" and "las"
Another member posted a question regarding this. I answered it over three hours ago. There has been a lot of activity since then, but nobody stopped by to see this. I think if I put this up as a question, and people see my avatar, they may be interested. ¡Ojalá!
This is not too hard.
For "people words" Most words referring to females end in "a" the article is "la" plural "las"
"la chica" "las chicas" "la doctora" "las doctoras.
Most people words referring to males will end in "o" the article is "el", the plural "los"
"el chico" "los chicos" "el obrero" "los obreros"
People words ending in "ista" or "eta" are both masculine and feminine.
El turista, la turista el atleta, la atleta.
Note: Any word that refers to a male or female will use the proper article regardless of the ending..
Ex. El hombre La mujer
Inanimate things.
Most words ending in "o" are masculine. --el sombrero, el cuaderno, el libro etc.
Most notable exception is "la mano" (the hand)
All words ending in "or" are masculine, whether a "people" word or an inanimate object.
Ex. el motor, el profesor, el doctor
Most words ending in "s" are masculine. El autobús, el país
All words (inanimate objects) ending in "ema" or "ama" are masculine. These words came over from the Greek with their masculine genders. "Programa, telegrama, drama, tema, panorama, etc.
Mostwords ending in"a" are feminine. La computadora, la lavadora la escuela, etc.
Most notable exception is "el mapa:
All words ending in "dad" "tad" and "ión" are feminine. Many are cognates.
Libertad, ciudad, comunidad, nacionalidad, and many more.
Acción, nación, conversación, and many more which are cognates.
There are some feminine words ending in a, but start with a stressed "a" These will get the masculine article in the singular because it sounds better. However in the plural the feminine "las" will be used.
EX. el agua--las aguas el águila--las águilas, el ama de casa--las amas de casa.
I have read some of the long scholarly versions, but they are usually confusing to the beginner. What I did not do was to give the English for my examples. Use "el diccionario" if you don't know a word. SD has a good one. Buena suerte. smile

Edit.
I forgot to add one category. Words ending in "e" can be either masculine or feminine.
"la gente" (people in general) and "el puente" "la fuente" (the flower) The gender must be memorized when you learn the word.
3 Answers
Letters that are most frequently masculine are LONERS (anything ending in those letters)
In correction of what was said about words ending in -ión, the following words ending in -ión are masculine (it should be words that end in -ción and -sión are all feminine):
El camión, el avión, el embrión, el anfitrión, el centurión. I'm sure there are others, but those are what I know.
Según los diagramas en el programa, la fama de la cama de la dama vestida en la piyama con las llamas hechas de escamas rojas era una rama importante de la gama de las tramas en el panorama del drama.
According to the diagrams in the program, the fame of the bed of the lady dressed in the pajamas with flames made of red scales was an important branch of the gamut of themes in the panorama of the drama.

Members that are "beginners " could do some exercises here using all of these
definite articles and even throw in a few indefinite ones , give it a go guys.