Are there rules or suggestions on how to use the voting system?
The reddiquette is kinda clear on how to use the voting system, though admittedly they pretty much abandoned that document and can't be arsed to inform their users about it. In short, it's about using voting as a form of quality control, not as a form of "like" and "dislike". I really like that system. I will paste the relevant parts of the reddiquette below.
In general, I really favor the idea that one should never downvote simply for differing opinion. If a stance is clearly formulated and well argumented, you shouldn't downvote that post simply to show disagreement. One should upvote comments that are the result of great effort and enrichment of discussion, even when one does not 100% agree with the content of that comment.
Voting on posts works a little bit different, though. One should downvote what is not appropriate for a sub. For example posting a very good and well written recipe for a pizza should be upvoted in the pizza sub, but downvoted in the lasagna sub.
I guess it could be possibly confusing that voting works differently for comments and posts. It is of course way easier for any given user to just upvote anything that they like, and downvote anything they don't. But that's not a good idea at all. If you simply downvote anything you don't like, you'll end with a filter bubble, an echo chamber, where the most visible and highest voted comments are always what the majority thinks is right.
I think it should be about quality, not quantity. Votes should be given for quality posts, and for quality comments.
Are there any rules or something about how it should be done here on this instance?
Here are the relevant parts regarding voting from the [Reddiquette](https://www.reddithelp.com/en/categories/reddit-101/reddit-basics/reddiquette):
> **PLEASE DO**
> Vote. If you think something contributes to conversation, upvote it. If you think it does not contribute to the subreddit it is posted in or is off-topic in a particular community, downvote it.
> **PLEASE DON'T**
> Downvote an otherwise acceptable post because you don't personally like it. Think before you downvote and take a moment to ensure you're downvoting someone because they are not contributing to the community dialogue or discussion. If you simply take a moment to stop, think and examine your reasons for downvoting, rather than doing so out of an emotional reaction, you will ensure that your downvotes are given for good reasons.
> Mass downvote someone else's posts. If it really is the content you have a problem with (as opposed to the person), by all means vote it down when you come upon it. But don't go out of your way to seek out an enemy's posts.
> Moderate a story based on your opinion of its source. Quality of content is more important than who created it.
> Upvote or downvote based just on the person that posted it. Don't upvote or downvote comments and posts just because the poster's username is familiar to you. Make your vote based on the content.
> Report posts just because you do not like them. You should only be using the report button if the post breaks the subreddit rules.