These open league tips are based on the sim engine and salary structure as of September 2014.
These are only suggestions, you can build a successful team without following all of these guidelines.
Draft 9 players that total at least $41M and no more than 17,000 minutes.
When the league starts, send the other 3 players to the inactive list and replace them with the computer generated rookies.
The rookies can be identified by using their position effectiveness, per%/mid%/pnt%, ppg/rpg/apg.
As much as possible, draft players that are 100% effective at multiple positions and have a midrange% less than 45.
Make sure you have 2 players on the court at all times with a usage% of at least 22.1% and an eFG% of at least 48% (or 1 player with a usage% of at least 32.5% and an eFG% of at least 48%).
Your starters should total at least: 50% ast, 30% oReb, 70% dReb, 90% usage, 200 3PM, and at least 3 starters should have a defensive rating of at least 70.
Try to avoid drafting players who are foul prone or have an eFG% less than 45%.
Generally, I'd recommend running an uptempo offense and a half court defense.
You can find some good values with partial season players.
Usually, the mop up lineup will be the 5 players with the lowest amount of target minutes.
Here are some posts that give more detailed analysis:
Also, you may see some people on the forums complaining about the sim being a complete crap shoot or that defense doesn't matter. Neither of these are true.