What follows are the criteria I use in determining how I vote at Wikipedia:Requests for adminship. My criteria describe an "ideal candidate" and in certain cases, when it is obvious that granting the candidate adminship will be a net positive to the project, I will relax them.
Tenure
editLength of tenure does not qualify an editor to become a sysop. However, I don't believe it is possible to become conversant in Wikipedia policy in a short period of time. I'm unlikely to support any candidate who has not been registered for at least 12 months and has made significant contributions to the project throughout that time period. I personally felt unqualified after three years as an editor.
Edit counts
editEdit counts are often cited as a metric by which experience can be measured. However, not all edits are equal. The purpose of the Wikipedia project is to create an encyclopedia and one of the first things I look for is the user's commitment to content creation within article space. I consider 5,000 non-automated edits within article space a reasonable expectation for any prospective sysop.
Demonstration of understaning of deletion policy
editContributions to AfD
editOne of the main functions of a sysop is the deletion of articles. The candidate should have shown significant contributions to Wikipedia:Articles for deletion and should have demonstrated knowledge of wikipedia policy in their contributions.
CSD tagging
editCategory:Candidates for speedy deletion is always a minefield of incorrectly tagged articles and borderline cases. I am unlikely to support a candidate who has little experience of Wikipedia:New pages patrol. Similarly, if the candidate shows significant evidence of incorrect tagging or premature tagging. (Everyone makes mistakes.)
Block log
editI am unlikely to support anyone with anything other than a pristine block log.
Maturity
editA bit of a vague area here. I'd prefer candidates to be of the age of majority. More importantly, they should act as if they are, both in their contributions to content creation and in their interactions with other editors. On becoming a Sysop, editors typically begin to experience more extreme forms of interactions with other editors than they might have previously experienced. It is crucial that they are able to deal with challenging behaviour while remaining personally detached.
Sincerity of candidacy
editThe whole point of the Wikipedia project is to create a credible encyclopedia. This must also be the main motivation of its sysops. If it is apparent that the candidate's motivation is otherwise, for example he wants to be the Dungeon Master of a Massively multiplayer online role-playing game, I'm unlikely to support them.