As you are probably aware, Spanish owes a significant portion of its vocabulary to Latin. An interesting difference however is that Spanish has only two genders for nouns - feminine and masculine. The coincidence of the Spanish gender with that of Latin is very high (in fact, so far I've not come across a Spanish noun which has the opposite gender in Latin).
Now, as a native speaker of Spanish, I can sometimes sense the gender (m or f) of a Latin word I encounter for the first time by drawing from Spanish. This is quite useful, as I can then try to get the declension, mode and understand its meaning, without having to go to a dictionary.
For instance, if I read insulae, my Spanish tells me this is feminine. If I read, fluvium, my Spanish tells me this is masculine. But if I read altaris, I would say this is masculine. And yet, it is neuter!
Thus, when it comes to neuter nouns in Latin, my method utterly fails, because there are no neuter nouns in Spanish! Thus, I am looking for some intuitive way, a rule of thumb, or way of sensing when a Latin noun might be neuter. Is there such a thing? Or is this ultimately arbitrary, and then purely memory?
More generally, is there a way to predict the gender of nouns? At least in Spanish, as far as I know, there is no ontological underpinning to the fact that a cuchara (spoon) is feminine and a tenedor (fork) is masculine. Thus, it might well be that the gender of many Latin nouns is so because it is so. Memorā!