There are multiple ways of winning in this game and I have never found a single winning strategy that I could call best. But there are for sure good strategies and bad, you just have to choose one and try it out to see if it works for you. There are winning strategies that are easy to implement and that are tried and proven, and there are others that are very difficult to implement but can be totally baffling to the opposition because it is seldom, or even never seen.
I spend a lot of time thinking up new strategies, then I take those strategies to D II and try them out. How hard is it to recruit the players that I need to execute my strategy? How hard is it to maximize my practice time to get my key players ready? How long does it take to build a team and get it deep into the playoffs using the new strategy?
These are the type things that I'm asking myself concerning my strategy, but there are other questions that you should ask yourself.
How does my recruiting compare to the top coaches at my division in the world I'm playing in? If I'm not in the top 10 then how can I improve?
How well do my players develop compared to the top teams, if I recruit well but my player's attributes fall behind over their career then how can that be improved?
You should sit down and list all of the things that you control in the game and think of ways to find out if your settings are the best they possibly can be for your chosen strategy. This generally means testing, most of the top coaches have spent a lot of time and money testing their settings under various situations looking for an edge. The cool thing about it is that there is no one right answer for everyone or every strategy, there are a lot of settings that will improve any team, but many of them are team and strategy specific. It is the coaches job to figure out what those settings need to be for his/her team to reach peak performance.
My advice to anyone playing this game is to decide on a strategy and see if you can get deep into the playoffs with a top 10 roster, if you can do it with a top 15 roster then you are probably onto something good. If not then according to how far back you are make some appropriate sized tweaks and see if your team gets better or worse. Once you are deep in the playoffs and in striking range it will either be a matter of recruiting better, developing players better, or doing tiny tweaks to your strategy.
In my experience it is hard to win a championship, even with a really good strategy, if you are not at least in the top 15 rated roster by the GUESS report. It is very rare outside of the top 10. If you have the top roster and you still can't win a championship, then you need to tweak your strategy.