After reading about lineup creation, player positions, and basics of formations, you should have a solid grounding to select your formation for the season. Here are specific recommendations for 9v9.
3-2-3
Pros:
- 4 spots to put less developed players (wings and fullbacks)
- Very strong center
- Excellent width
- Provides good passing and clearing options
- Tends to isolate your forward with opposing centerback
- Transitions well to the popular 4-3-3 formation at 11v11
Cons:
- Higher work rate needed from center mids
- Four strong players needed on the field at all times
This has become the more popular formation among most club organizations however I really like it at the rec level for separate reasons. It matches up very well with the traditionally more popular 3-3-2 formation.
3-3-2
Pros:
- Balanced offense and defense
- 5 spots to put less developed players (outside fullbacks/mids and either forward)
Cons:
- Does not match up well against 3-2-3 in the middle of the field
- Less offensive / easier to cover
Other formations and opinions:
http://www.youthsoccer101plans.com/9v9-formations.html
Super helpful insight on positioning! Sometimes this is tricky to figure out when moving up every couple years to more players on the field. Like your pros and cons of each formation.