I tend to focus on one aspect of a game. How do I take the necessary balanced approach that's necessary in games like Seven Wonders?
7 Wonders is a game that rewards flexibility.  Moreso than anything else, the winner will be the one who has identified the key weaknesses in the rest of the players and exploits that.

The problem that many players have is they think "I'll go science" or "I'll go military" or some other strategy.  Alternatively, they just pick the juciest looking card every time, with no thought to the ultimate purpose for the card.

Both of these methods are bad.  7 Wonders is a game about optimising your draft options.  Sometimes that means forgoing wonder levels.  Other times that means forgoing brown resources and other times that means neglecting yellow buildings.  In all cases, what you should realise is that while your civ has strengths, your opponents are revealing vital information about their game plans in each and every draft.

In one 7 Wonders game I played I was Rhodes (who are very, very strong).  I went a very early military building and then pure science and won.  The reason that I did that was that I identified early on that nobody was going science and my neighbours were scared of me going military.  They went heavy brown resources and yellow/blue buildings.  In another game I didn't get a single science card but picked up early game blue cards (which were being ignored by the board), enough military to get my 18 points and denied my neighbours the use of their marketplaces (which were both pointing away from me) by snagging and preventing key resources for their strategy.

In all cases, realising that the game was not multiplayer solitaire was enough to give me resounding wins.  Remember not to fixate on a strategy, rather, fixate on your opponents strategies.  You won't be able to counter them all, but you will be able to identify the gaps in demand and exploit them.