I've been wondering if it is appropriate for me to upvote questions and answers. I know that native speakers upvote good questions and answers. But being a non-native, I've been feeling a bit hesitant to upvote questions and answers, especially answers (I've been upvoting questions here and there). I want to upvote questions when they are those that I'm also curious about, and I want to upvote comments or answers when I learned something new from them. What do you think?
Upvoting is not a crime! However, if you do so for one particular contributor, ELL may consider that as serial upvoting.
So, avoid doing these things while upvoting -
Don't do it too frequently - say in one day, you upvoted several dozens of them
Don't do it for one particular user - say you upvoted only my questions/answers
The best thing is - be neutral. If you like questions/answers, upvote them by all means but it should come as a natural gesture.
Upvoting comments in any frequency is not an issue at all. But still, stay neutral.
Here's how I would handle your situation: If the answer was recently posted, wait a day or two. See how others in the community respond. If no one seems to be commenting with negative feedback, then go ahead and upvote the answer.
You could also use the "favorite" button on the question to help you remember which answers you want to go back and check again later.
By the way, I think your caution is commendable. It doesn't happen too often, but, on occasion, I have seen a few bad answers get upvotes. I think that undermines the credibility of this site, so thank you for wanting to vote judiciously.