One of the things I have noticed is that there are different seasons this site goes through from time to time. When I got here it was extremely busy, however, there were some users that were not very encouraging, in fact, they were quite discouraging but just a few. Up-votes and down-votes were both quite prevalent at that time.
There have been various seasons since then different to the one we have now.
Currently, we do have a lot of non-regular users passing through and trying the site out. It appears to me that a fair portion of these users are not invested as you suggest. This is a season where people are trying out the site, but the number that will stick appears to me to be smaller than normal and that is just the way it is right now which is okay. It is these users that can come back from time to time. As things change, we will see more users jump in and answer questions. It is just a season that will change.
You are absolutely right about up-voting.
When I got to this site, I was strongly encouraged by the longer term users and moderators. It is something I especially appreciate because of the occasional attacks that would come along back then. Today, we have a much friendlier crowd and we can forget that we must steer this ship toward the horizon we wish. I still like to be encouraging and I advise users to do the same.
For a season, up-votes were quite common and down-votes far less. Today, it remains much the same with less voting overall. A few users are issuing down-votes kind of regularly which has been in line with how the site is supposed to work. I was try to discourage non-constructive down-votes. These are down-votes without a comment or guidance to making the question or answer better. I still try and add some guidance and encourage people to do the same. As part of this, when an answer is technically good but there may be an element missing, I like to simply add a comment.
I encourage people to add guidance to the questions and answers to help make them better.
I like to encourage specific users with up-votes and guidance. While encouragement should be as even-handed as possible, there are some users that stand out. @JosipIvic is one of them. No question.
I often add comments even when the answer is complete. The reason for this is that we are all people and should be encouraged, engaged, and simply cheered. We are being reminded of that here.
What to look for.
There will be for a while a wave of users that are looking only to get their questions answered. That has been and will always be the way. However, users that answer questions are interested in this site for whatever reason that motivates them. This where the bulk of the encouragement will benefit this site.
One bit of advice I can give right now.
While I can be a bit famous for longer answers which has sparked a bit of controversy, shorter answers are great too. @JohnConde is famous for extremely succinct answers. In fact, he cracks me up! He comes in with a perspective that is unique and I as well as others appreciate. We seem to be a polar ends of the spectrum and this is okay. However, for most of the answers I advise a bit more or less depending upon your personality. Here is a short list of what I mean.
Up-votes are a two way street.
Answers can encourage up-votes as much as users participating.
Answers that are answered in a link. It is good to link to other pages. I encourage it. However, if the answer itself does not provide a solution and the link is broken as they can often become, then the answer is of no value later. It is best to always put something into the answer. It shows effort and care which encourages up-votes.
Answers that do not contain the reason why. It is good to provide a solution. However, if the OP does not know the Why?, then the answer is missing an extremely valuable component. The OP can be knowledgeable and not require the why, however, others along the way may not be as knowledgeable. For this reason, it is good to explain why the OP has a problem and how the answer addresses this. Explanations of the why go a long way to encouraging up-votes.
Answers short on detail. Some answers are particularly short on detail. Again, the OP may not need the detail, but others will. Detailed answers go a long way to encouraging up-votes.
Answers that are dated. We have all seen them. These are answers that are based on older advice that is either simply dated or completely wrong as a result. It is important that answers steer the OP in the right direction. It is okay and advisable to explain how the OP is misguided if they are. It is also of more value and appreciated when the answer explains how things have changed. This is appreciated by many and will encourage up-votes.
Answers that are simply parroted echos. Sometimes it makes sense to repeat what others have said. That is a given. However, as I often say, there are a ton of sites with parroted answers that are just plain wrong or misleading. I advise resisting parrot answers and putting some real-world thought and experience into the answer. It sometimes is advisable to say why the traditional answer is parroted, wrong, or misleading. Again, the detail will encourage up-votes.
Answers that seem to be missing research. Yes. Short answers are great! However, answers that do not show a clear amount of research behind them can really discourage up-votes. It is possible to have a technically complete and correct answer. Then another answer that provides the research behind the answer comes along the way. The answer with the research, even when not as technically complete or clear, can receive more up-votes simply as appreciation for the effort.
Answers that do not seem to have much effort in them. This is a bit of a catch-all for some of my list, however, effort can be read. I encourage more than the minimum effort be put into answers. It does not have to be a lot. It just has to signal that you give a rat's patootie. (Which we all do. Right??)
Answers without personality. We all have one. Share it. Put your personality in your answers. Humor works too! I have gotten up-votes for weirdness and silliness as much as anything else. Dive in and put yourself into the answer.
This is just a short list. I am sure there are other ways that an answer can encourage up-votes. Feel free to comment on ways you think answers can be improved.
I have to admit being distracted and time has become precious lately. I have not had much time to give. This is temporary of course. We all get that way. Perhaps, in my case and others I assume too, when we are short on time, the best thing we can do is encouragement. Up-votes, reviews of question and answers to provide guidance, and just plain 'ole encouragement. +1 comments are not exactly appropriate, however, I do like to take the time and discover what it is about a user, question, or answer I like and just say so in a comment. More verbose attaboy's are good. Perhaps when we are short on time, we can focus more on just doing the WWJD thing. (Not to introduce religion into the mix. Pick your own motivation. However, if you can turn water into wine then I am sure you will get a lot of up-votes if you share. Mom always says it is good to share!)
Remember that seasons come and go. It is just a matter of time when this site changes again. There are forces external to this site that influences things. However, we must remember and remind ourselves of how we have influence here too and can solidly steer the direction of this site. For a while, there were trolls, now there are not. That was the user base saying that trolling is not acceptable. In the same way, we can say what we want this site to be. We can steer this ship toward warn horizons with lush islands, grass skirts, and friendly natives.
I firmly believe if you are a webmaster, this is the place to be. It is by far the friendliest group of people out there affirming what I have always said. Webmasters are amongst the best people in the world. Not sure why. I will just accept it and encourage it. Grog anyone?