After achieving 500 rep users can
Access first posts and late answers review queues
This post (will) contain examples of how to handle first posts and late answers. There's not much difference, except late answers are always ... answers, and there seems to be a higher chance of spam.
As a wiki post, consider it as a draft and feel free edit at will.
The options you have are
Upvote and approve
I've been doing this more often, lately. It's a way of showing the user they're on the right track.
Downvote and approve
I don't do this ever. Would others like to comment?
Skip the post
Do this if you're not sure what to do with it. If you want to see what others do, you can open the post (the question title links to the question) and star it (make it a favorite). Come back to it in a day or so to see that happened. You can also click the "history" link to see all the reviews.
Another reason to skip it is if you think you're not being impartial. This happens to me (andy256) sometimes when I've already answered a question and then find it on the review queue.
Approve without comment
Often other users have already posted comments or answers by the time you see the post on the queue. If any concerns have already been addressed then it makes sense to just approve it.
On the other hand, some new users just seem to get it. So much so that a nice encouraging welcome message seems out of place. If you're not leaving a nice message, consider an up vote. I (andy256) have done this more often, lately.
New users with 101 rep have come from another site, so they often don't need guidance.
Flag the post
After clicking Flag you get several options. In my understanding, most of them lead to the post getting onto other review queues, or to a queue for moderator attention. Flag the post when you think there's something wrong with it. Sometimes it seems worthwhile to leave a comment explaining that you're flagging the post and what the user could do about it, but only do this if the post seems salvageable. If not then don't try to discuss it with the poster, just flag it and let others deal with it. Some flag actions seem to automatically create a downvote (spam questions, for example - keep flagging them, after 6 flags they get deleted).
When a post should have been a comment (the newbie doesn't have enough rep to post comments) you can flag for moderator attention, and politely ask them to convert it to a comment. Leave a comment for the user to explain.
Approve with a comment
If you include [Bicycles.SE] in your comment it gets converted to link to the site. I like to add @username (I learned it on [English.se]) because it gives an example of how to address a user in comments (it has no effect in this case, but it is an example). Like this
Welcome to [Bicycles.SE] @username.
If the user has no bronze badges, then they haven't taken the tour. If they do have a bronze then check if it's the [informed] badge. If they haven't taken the tour then I say something like (Móż also uses similar wording)
Welcome to [Bicycles.SE] @username. We recommend that new users take the [tour] so that you can make best use of the site.
If it's a question I add at the end of that sentence
and since you're asking, see [ask].
The [ask] part gets converted to a link to Help Center > Asking.
If it's an answer I add at the end of that sentence
and since you're answering, see [answer].
The [answer] part gets converted to a link to Help Center > Answering.
Here are some examples of comments on first posts, and a few snippets
Example from dlu. This is a nice example showing positive language and a response (seemingly) written specifically for the post.
Welcome to Bicycles! You may want to spend some time on the tour to get an idea of how Stack Exchange works – we encourage answers to questions supported by evidence. The idea is that we can learn from each other's experience and knowledge. It also helps to take care with formatting and grammar in your answers. Readability counts.
When a post is a discussion instead of a question or answer (lately I've included the [tour] comment mentioned above)
Welcome to [Bicycles.SE] @username. This site is different - it's not a discussion (although you can use [chat](http://chat.stackexchange.com/rooms/214/the-velodrome) for that).
When an answer should be a question
To ask your own question, start at the [Ask Question](https://bicycles.stackexchange.com/questions/ask) link at the top right of the Questions page, and fire away. Also check out [ask], and do a search to see if your question has already been asked and answered.
When a post is the basis for an answer, but too short (from jimirings). The post was an answer to What to use to clean your chain (and cogs)?
Welcome to Bicycles SE. We're looking for answers with [more detail](https://bicycles.stackexchange.com/help/how-to-answer). Please consider expanding your answer to explain why auto body degreaser and simple green are good solutions for the OP's problem. You might also explain why the OP wouldn't want to use auto degreaser all the time. A short, one-line answer like this is likely to get downvoted, flagged for moderator intervention, and possibly deleted.
When a post should have been a comment
When you have enough [rep](https://bicycles.stackexchange.com/help/privileges) such a post could be made as a comment.
It is a site where good answers should become definitive references.
We're looking for answers with [more detail](https://bicycles.stackexchange.com/help/how-to-answer).
As this answer stands, it is likely to be downvoted and possibly deleted.
Also note that we ask that you [be nice](https://bicycles.stackexchange.com/help/be-nice) on this site.
Here is an example of a poor review: Safety comparison, downhill mountain bike vs. downhill ski. I (andy256) saw that it had parenting content, and mildly suggested that [parenting.se] would be more appropriate. Then I couldn't help myself and added an unhelpful comment.
A better approach might have been to edit the question, removing all parenting references, and leaving a question that just compared DH skiing and biking. The whole interaction would have been different after that.
And finally, a very nice review from rclocher3:
Hi Alan, and welcome to the site! We recommend all new users take the tour to get the most from the site, and since you volunteered an answer, it couldn't hurt to also read how to answer. Regarding your answer, electrical conduit is meant to be bent when installed, but I'm skeptical about bending handlebars the same way; handlebars have different metallurgy, because they're meant to be light, stiff, and strong. Of course someone might try using handlebars made from conduit ;) Again, welcome.