Almost every bilingual person feels distracted by the subtitles on the screen. I, for one, usually feel the translator misunderstood a phrase, (or is evidently not fluent in both languages). In the event of subtitling videos with Spanish audio into English, there is an additional difficulty: Spanish will take up more words or characters, while the English version may prove to be too short, and in the end the scene seems to lack the necessary text support.
There are a number of things to be taken into account, which might contribute to attaining better results:

- maximum number of characters allowed is usually 36 or thereabouts. Here, Spanish audio into English subtitles may prove too short. Try playing the scene again, to find if you can better wrap the implied meaning into the lines translated. English into Spanish subtitles will present the difficulty of the lines resulting too long. Do not waste time trying to shorten them immediately. I find it easier to make adjustments at the end of each scene, as I read the lines over and over and watch the sequence to grasp the meaning of it all.

- scene subtitles need to follow the thread of action shown. You may need to re-think and re-word the subtitle until it fits perfectly into the sequence.

- subtitles in advance look awful. Avoid filling up empty spaces with subtitles corresponding to the following scene. If in doubt, it is better to leave the subtitle for a few more seconds, instead of spoiling anticipation.

- Should slang be translated? This will depend on what the producer/subtitling company prefers. Some of them reject the "Slang for Slang idea". This allows the translator to offer a free version of what the phrase or word means, always honoring the original meaning, of course. If, however, you are asked to use "slang for slang", then you may make use of localized dictionaries offering equivalents for slang expressions.

- The same goes for idioms, sayings, etc. Google the idiom or make a wild guess and then google your guess. There's a good chance you'll come up with an equivalent.

In my view, subtitling deserves a category of its own within translation. Here, academicism will not do, and it is more a question of sensing the environment and setting, to come up with audience-friendly, colloquial, apt equivalents to the original audio.