Many new users are unsure how to pick their lineups. One way to start is by listing your roster by position, and selecting the highest paid baller for each position as your starter, the next highest for your backup, and so on. However, you'll probably also want to consider the age of your players; younger players will train faster, and will be around for longer, so you should give them some court time so they'll become better.
Positions
C - Center: Normally plays close to the basket and is responsible for getting rebounds and blocking shots.
PF - Power Forward: Usually the bigger, stronger forward who plays close to the basket and is responsible for rebounding and inside scoring.
SF - Small Forward: Usually bigger than the guards but smaller than the power forward; responsibilities include both inside and outside work.
SG - Shooting Guard: Generally, the player who takes the majority of the shots from the perimeter, many of which are three-point attempts.
PG - Point Guard: Usually a team's floor leader, who initiates the offense and controls the tempo of the game.
Training in BB is designed to allow managers to create unique players. No skill is completely useless for any position! Here's a rough idea of skills needed for each position:
Center
(1) Inside Shot, Inside Defense, Rebounds
(2) Blocks
(3) Handling, Passing
Power Forward
(1) Inside Shot, Inside Defense
(2) Rebounds, Blocks
(3) Driving, Passing
(4) Jump Shot, Handling
Small Forward
(1) Jump Shot, Jump Range, Outside Defense
(2) Handling, Passing, Driving
(3) Inside Shot, Inside Defense
(4) Rebounding
Shooting Guard
(1) Jump Shot, Jump Range
(2) Handling, Passing,
(3) Driving, Outside Defense, Inside Shot
Point Guard
(1) Handling, Passing
(2) Outside Defense, Driving
(3) Jump Shot, Jump Range, Inside Shot