Here's an easy achievement for you and worth a good 70 points!
When the game starts (before you press start to go into the actual game menu), you will be in the "Campus Hoops" mode. From here, you will have control of a solo player where you can shoot around on the black top. To earn this achievement, you must make 20 consecutive baskets, however dunks do not count.
Simply stand directly next to the basket and do a simple layout and/or 1-2 foot shots. They are very high percentage shots (I didn't miss a single one), plus you will be able to grab the ball again and setup for your next shot quickly. When shooting, just press the X button, but do not press the Right Trigger (as this will make your player dunk and dunks are not counted).
You should be 70 points richer in just about 2 minutes.