Probably should consider these points for a moderator.
A user that regularly visits and contributes to the forum is typically a prime candidate for a moderator role. Other members of the community already know them, they understand what is acceptable and what is not, and a sustained rate of activity actually proves that they aren’t fly-by-nighters - in other words, they are reliable.
Generally, they are very knowledgeable about the subject matter of the forum. For example, you would expect the person to provide a certain degree of insight and well thought out messages rather than countless one line posts; “I agree!”, “Well said!”, and so on don’t cut it. Once they are elevated to the position of moderator, they will be an authority on the matter, so you want them to lead by example. Their new rank or username colour - or whatever is associated with the new position - will set them apart from the rest, and the readers of the forum will subconsciously take extra notice of what a moderator (or administrator) has to say.
Generally, post count should not play a part. If the user you want to promote has been active over a long period, then this will probably be reflected in their post count. Be aware though, that promoting a user with a low post count will draw more attention to the selection than promoting a user with a high post count. While both may be equally deserving, the user with a higher post count may feel hardly done by because it would appear that they have contributed more to the forum.
There are other factors you may need to consider, such as command of the language or how much time you will want the user to commit to moderating, but these are very much dependent on the style of your forum and tend not to be an issue.
*** I never thought about how mods are chosen before so I googled a bit on what makes a good moderator.***
I hope this helps.
