In our Shackled City Campaign, I play a Sword and Board fighter. Keep in mind that I "cheated" at higher levels and picked up an Animated Shield, so I could use my main weapon two-handed.
I did not pick up the Weapon Focus feat chain. Instead, I concentrated on getting basically all the other fighter bonus feats out there (with, naturally, a lot of exceptions).
Combat Expertise, Improved Trip, Combat Reflexes, Improved Unarmed, Improved Grapple (very useful under the right circumstances), Defensive Throw* (Complete Warrior), Dodge, Mobility, Blind Fight, Quick Draw, Defensive Sweep (PHB II, very recent addition to the character) and some none-fighter bonus feats: Run, Iron Will (with 25 point buy, I had to sacrifice wisdom and charisma)
The net result was that I was prepared for most types of enemies. I could run to catch enemy archers or wizards (without opening myself up to sneak attacks or other nasty effects). I can go into grapple against a lot of dangerous opponents (especially spellcasters).
I can always draw the weapon I need for the job (Holy Cold Iron Longsword +2 is my primary weapons, but if required, I can pick up my Admantite Battleaxe of Construct Bane or my Silver Guisarme of Undead Bane).
*For use of Defensive Throw, I suggest using a tripping weapon as primary weapon (Flail). Thanks to the Cheating, err Animated Shield, I can use my unarmed attack to trip missing opponents, but normally, you would (depending on your DM's interpretation) not allowed to make trip attack while wielding a weapon.
At this level, I am actually considering if I should try to pick up Weaon Focus, but I decided against it - it is against the concept of the fighter and it would also take to long to get a significant benefit from it. I instead picked up a home brew PrC, Master of Martial Arts (
http://www.gweb.de/ttt/news/news.php?exns=1&xnsmid=7), which grants some nice benefits along the theme of my Fighter (1-3/day a bonus feat for one encounter, improved unarmed damage and combat speed, AC Bonus when fighting lightly armed - everything to be prepared in situations where you aren't actually prepared...)
So, my advice: If you want more than just hitting the hardest and instead want to experiment (and "win") with combat techniques available in D&D, ignore Weapon Focus and instead focus on all the nice Improved [Insert Combat Option here] feats. If you want to focus a bit more on your shield, the Shield Specialisation feat chain is certainly a good choice (and it can be combined with the combat technique feats, you just have to be a more picky)