There is no general rule to determine the gender of a noun based on its spelling, however, many endings are either deterministic or at least strong clues to know the gender.
Here are some statistics based on a list of French words extracted from the Lexique 3.80 database which contains words built from 64.7 millions words found in 218 books from 1950 to ...
The following paper posits a different set of rules which (when tested on their corpus) proved to be much more accurate than the "careful" principle:
Our proposal, then, is the following. In conjunction with a pedagogical norm which requires students at elementary levels of the study of French to produce only obligatory liaisons, we suggest that students ...
I good rule of thumb that I've learned in my college french class is that you use connaître as connaître + [article + noun]/proper name
Je connais John.
Je connais la physique.
Je connais la chose dont tu parles.
while savoir is used if what follows is an infinitive, conjunction, or question word.
Je sais conduire.
Je sais que tu es fatigué.
The comparison with German is not going to be very helpful, in general. Here are rules of thumb for French:
All reflexive and reciprocal verbs are conjugated with être
Most of the rest of the verbs are conjugated with avoir
Except for a short list of verbs, which, when used intransitively, are conjugated with être
The rule of thumb for the short list is ...
The rule of thumb that would apply here is that prepositions go with lui, never le. Pour is a preposition, so it's pour lui. Examples of lui used with other prepositions: de lui, avec lui, sans lui, vers lui (approximately "of him, with him, without him, towards him"). In contrast, le in Je vais le voir is not used with a preposition.
The form lui has other ...
The words that are translated as "him" in your two examples do not have the same function. In Je vais le voir, le stands in for a third-person singular masculine direct object. Generally speaking, the direct object is not prefixed with a preposition, when a verb is applied to it. Thus, these are acceptable substitutions:
Je vois la poule. ➔ Je la vois. (La ...
There's really no way to avoid grammar when answering this question.
Le is "him" as a direct object, which means that "him" is the person being affected directly by the verb: I see him (Je le vois), I know him (Je le connais), I hate him (Je le déteste).
Lui is "him" as an indirect object, meaning that "him" is not the direct object of the verb, but rather ...