Sjakkalle's admin criterion of whether he will support or oppose a candidate is:
Some of the criteria Sjakkalle does not apply include:
OK, my criterion says little, so here is some clarification (or perhaps it is more fog).
Edit count is a very objective criterion, and it is true that more edits usually mean more experience. But while it can be an OK place to get a first impression, it is a poor place to stop. In particular
Now with that said, an "average" nominee would need something around 1500 edits, which means that a person with less than 500 almost certainly has too little, while one with over 3000 almost always has enough. But there is no barrier between 1499 and 1500.
Again, time spent is an objective criterion, and again it is a mistake to use a D&D like absolute guideline on it. In general, I would expect an admin nominee to have something around 2 months or 3 months.
Experience with the project is important, but as I said above, is a function of more things than just number of edits and time spent. Has the contributor made some very good contributions to articles? Has the contributor been an active participant in debates and discussions (Village Pump, Deletion, and so on). Maybe the contributor has been active in fighting vandalism at RecentChanges. I set no real demand on participation in any, but it should be demonstrated that they know what Wikipedia is about. There should be some variation in the contributions, specialization is fine, but some contributions outside the field of specialization is also needed.
How a candidate handles conflicts is more important. Some candidates can honestly say that they have been able to avoid conflict. That's good, I will not hold that against them. I don't demand a battle scar. In most cases, such a user is one which I have had very little interaction with or have seen very little however, so that would mean I wouldn't vote in the RFA anyway. (Typically such RFAs for contributors with great contributions to articles but with little participation in the Wikipedia namespace where most of the conflicts take place are successful, but have very few votes, around 20, sometimes less.)
But having demonstrated good conduct in times of conflict is definitely a plus. An admin who is fairly active will run into conflicts, and it will be good to know that the users equipped with block-buttons can keep their head cool under fire. Also, it is not a really good thing to always dodge conflict, because when faced with trolls and vandals, a firm administrator is needed to put a stop to it. (This does not mean that an admin who shies away from conflict is unfit for the job, it just means that they aren't very active on the front lines.)
A candidate who is prone to making angry remarks at people who disagree with him or her is not such a good candidate. Some angry remarks or misplaced criticism are OK, everyone loses their cool occasionally, but such incidents should be the exception, not the rule.
Candidates who aggressively challenge every oppose vote, rather than politely responding to them, are doing themselves a disservice. An admin must be able to take criticism.
Worse are cases of candidates who have made trolling comments, personal attacks, or used foul language at anybody, including people who have made trolling comments, personal attacks and foul language against them. An administrator will run into trolls, vandals and rude people, and has to be able to tackle this, without decending to such a level. Wikipedia:Civility is important, and admins must follow it. Now, these bad things go over, having a history of foul language in the past, and then having improved the behavior is possible. That means a delay to the adminship, not eternal banishment from it.
Some admin candidates have foolishly vandalized something, or inserted some other nonsense due to boredome most likely, and when that happens, the RFA usually fails. I cut a little bit of slack because I don't want to make a too big distinguishment between those who get caught and those who don't. One "harmless" incident (e.g. nominating April Fools Day for deletion on April 1) in the past month won't knock my support vote away, a few "harmless" ones might however. A "harmful" incident (e.g. vandalizing a page with foul language to make an attack on someone) in the past month is more serious.
The candidate must have demonstrated that it's a good thing to make them an administrator.