The Easiest Way I found to do this was to start working on it as soon as your sim reaches (or starts at) the "Child" stage.
There are 4 relatively simple aspirations a child can complete that mostly involve getting the child skills (Creativity, Mental, Social, Motor) up to 10.
If you don't think you will have the time to finish them in the time your sim has left as a child, be sure to have them drink a potion of youth (1500 aspiration points) or turn off aging (this may not effect sims until adulthood, can someone confirm?)
Once you finish all 4 you can allow them to age up to "Teen" and select a final aspiration. You sim will have the rest of their life to finish this one, so there's no hurry.
Once the 5th one is complete, your achievement will unlock.
I coupled this with "The Most Interesting Sim In the World"
When you have 5 aspirations complete, the 5 traits you've won, in addition to the 3 your sims will get by adulthood, you will only need to spend your now vast supply of aspiration points to buy 4 more. They cost as little as 500 so you won't have trouble getting 12.