A guide to
Aspirations and Reward Traits has been covered. It features things you might need to know before joining, like if it requires a career, and states the full amount of Satisfaction you'll receive. Last, it discusses the bonus and reward traits associated with each to help you plan your Sims. I hope you like the layout
From this you might learn a good order for pursing things. Maybe take one that requires a career, then grab the mansion baron and/or Fabulously wealthy to grab a bonus. When you've got several skills or been in a couple of Careers, go for Renaissance Sim. You can sometimes have Milestones complete before you get to them, although there are numerous objectives that only start counting once you hit the milestone.
Children of Sims get a real leg up if you can complete one or more aspirations with them, as their bonus traits all boost adult skills. So, like a Sim who went to University in TS3, Children in TS4 will be able to do things faster as teens and adults than regular Sims from being raised well and pursuing goals in the game.
Special Thanks to Nutella for unexpectedly sending me every Milestone step and total Satisfaction so that I could summarize them for you all.