Those that win, plan. Those that don't, didn't 
"Winning" is
extremely subjective in Sims game, since it could theoretically go on forever with no end. In fact, it's so subjective that it's not one I even consider while I'm playing it. It's kind of like racing yourself down the stairs...you can't really win
or lose. So my largest piece of advice is to abandon such concepts as "winning" and "doing it right." If your Sims aren't keeling over from starvation or constantly peeing on the floor, you're in good shape.
Free will on high would definitely be easier. Sims know what they need and will go off to take care of their needs on their own, so it gives you one less thing to worry about (see my "keeling over from starvation or constantly peeing on the floor" comment
). If you'd rather have them do something else to fulfill those needs, it's easy enough to redirect them.
If your Sims aren't advancing in their careers at the rate you'd like them to, it's most likely due to one or more of 3 things: mood, skills, or friends. Checking their career panel should give you a heads up as to where your Sim is lacking. Your Sim will progress the fastest when the smiley faces look like this:
(only in green). If they look like this:
(in red), they will progress a lot slower. Luckily, fixing all 3 is a relatively easy process.
Mood: This is the easiest to fix. Before they go to bed for the night, try to get their needs as high as possible. Pay particular attention to Hygiene and Fun, as these two in particular you won't be able to increase at work. Also make sure they get plenty of rest before they go. The benefit of moodlets cannot be overstated here. Having a good bed and kitchen appliances will go a long way to keep their mood up throughout the day, and a good tv will increase their fun faster as well. And if you have access to laundry appliances,
use them. A 12 hour moodlet just for changing your clothes cannot be beat.
Friends: i.e. Your co-workers and boss. This is just as easy to fix. Simply see which ones need improving and select either "Chat with co-workers" or "Suck up to boss" options when at work (different careers may have different wording for these options). You should never allow your Sims to work under the "Business as usual" option, as there is almost always something better they could be doing with their time.
Skills: Definitely the hardest of the three, but not all that difficult in the long run. Possibly the easiest way to do this is to read books at the library (for skills that actually have books, Athletics does not). The library gives you a moodlet that allows you to read faster. For Athletics, do not train at the gym as there is currently a bug which makes leveling Athletics there difficult to impossible. Buy athletics equipment for your home, or if you have Ambitions installed you can use the equipment for free at the Fire Station. In a pinch, a television or radio will serve the purpose just fine.
Work related opportunities are also helpful, too. They will give you a bit of a boost to your career progress, and occasionally a nice bit of cash as well. When they come up at work, take them and complete them as soon as possible even if it means foregoing skill training while you do it.
