Criteria for ranking
It is very hard to list all possible issues that can prevent a beatmap for being ranked, since each beatmap is a unique creation. However, here are some general guidelines that a beatmap set should follow in order to be ranked:

- Perfectly timed. This means that your BPM and offset are spot-on, sliders end when they should, and notes are generally following a rhythm which is comprehendable by a player.
- Beat placement generally follows the time-distance-equality rule (holding Alt while placing beats or turning the Distance Snap icon on enforces this). This means you shouldn't have some fast notes with huge distance between them and/or closely placed but slow notes. This gets really confusing if the player isn't the person who designed the beatmap! Having some logic to the placement should be one of your goals. In Insane difficulty maps, this guideline might be relaxed a bit more.
- At least two difficulties per song is highly recommended, especially if one of them is rated with 4 or more difficulty stars (in the song selection screen). It is very preferrable that you include an easier version with 3 or less stars. There are a lot of players who are not so skilled at rhythm games - and this is one of the more difficult ones to get used to, so we should look at providing beatmaps which are passable for even beginners!
- Make sure you can pass the song, or at least its easier difficulties.
- The song should not be too long! Aim for 2-3 minutes maximum. Anything longer could get tiring. If you need help editing a song down to length, feel free to ask in the Beatmap Help forum. Use TV versions of opening/ending themes where possible.
- Use breaks where possible. Even if they are only 5-10 seconds, it allows a bit of recovery and hand repositioning for the players.
Try to keep osz files under 10mb, or 20mb if you include video.

Again, remember that there are can be many more possible problems with a beatmap. Pay attention to the tips when you open the Editor and the suggestions of the FAQ, Help pages and tutorial videos. You can also try viewing ranked beatmaps in the Editor to get an idea of what an approved beatmap can look and sound like.