What I did was during my 50 points against NJ with Lebron, by the time I had the 50 points, Shaq had about 15 boards (all of which were computer controlled). I just then used Shaq to score 10 points, then get 10 assists and voila achievement unlocked.
So if you're having trouble getting steals or boards, play a game on 12 min quarters with all sliders in your favour, and work towards a scoring achievement. By the time you're done, look at your players stats to see if any are in the double digits for boards or steals, and if so, just do 10 points & assists with that player.