I've played a fighter/wizard in Living Greyhawk since the start of the campaign. Eldritch Knight really made the character work. Right now (due to a recent conversion), he's exactly as he would be if built in 3.5 from the ground up: Fighter 1/Wizard 6/Spellsword 1/Eldritch Knight 9. Between a +14 BAB and 8th level spells, he's a powerful and effective character... but he requires a lot of finesse as a player.
Principle 1: You're not a primary caster--don't act like one. The combat abilities from Fighter, eldritch knight and spellsword have to pull their own weight from level 1 to level 20. If at level 17, I find myself acting like a straight-class wizard, I'm not using my character to his full potential. (Not to mention, he's not qualified to be a straight-caster wizard. Any competently built and played straight-caster 15 is far better than he is in a spellsling match. Two caster levels don't make up for a sub-par Int (the natural consequence of investing in strength and dex in a point buy system), and no feats spent on improving spell penetration or save DCs).
Principle 2: look for synergies. Several people in this thread have recommended an archer eldritch knight. With Complete Adventurer bringing Arrow Mind into the campaign, there's more synergy in archery than there used to be, but there's not as much as there is in melee. Polymorph, enlarge person, true strike, ray of enfeeblement (especially when combined with Improved Trip), blink (and greater blink--especially with Contingency), Iron Body, Arcane Strike, Whirling Blade, and--if your DM is insane enough to allow it--wraithstrike can pretty much all work together simultaneously to give you very good melee defenses and a good melee offense.
Principle 2.5: Arcane Strike has synergy with nearly everything. One of the nice things about the ability to dump spells for attack and damage bonuses is that you can afford to prep more specialized spells like banishment or Power Word: blind and you've still got a very good use for them if the only thing you fight is undead.
Principle 2.75: Why the synergies will focus on making you a better fighter instead of making you a better wizard: Round by round, you can only do one (or two if you count quickened spells) things. At the basic level, you can swing a sword or cast a spell. If you cast the spell, the ability to swing the sword will usually not help you as much as having more full caster levels would. (Even in BAB sensitive cases like scorching ray, it's usually better to have enough extra caster levels to be casting maximized scorching ray instead of empowered scorching ray than to hit the extra few percentage points of the time--if touch attacks weren't so easy, it might not be that way, but by mid levels, they're pretty much "don't roll a 1" even for a straight-class wizard). If you swing the sword, there are any number of ways that magic can help you swing that sword more effectively.
Principle 3: since your DCs will be unimpressive and your max spell level lower than a primary caster, don't bother with blasting spells. You'll be casting Ice Storm when straight casters are casting empowered fireballs. When you're casting empowered chain lightnings, they'll be casting empowered delayed blast fireballs. And their DCs will be higher and their Spell Pen rolls will be higher. Don't try to compete on that playing field. Go for spells that don't have saves, that have a good effect even on a failed save, or that target multiple opponents. Glitterdust is a good spell at low levels because it still reveals invisible or hiding creatures on a successful save and can target a group of enemies. Ray of enfeeblement is a good spell because there's no save and your BAB is better than an ordinary wizard's. Power Word Blind, Enervation, Otto's Irresistable Dance and Wall of force are all good spells because there is no save. (Enervation also reduces targets' ability checks making them more vulnerable to your feats like Improved Trip). Banishment is a good spell because it can have multiple targets and because you can crank the DC by using things like a silver holy symbol and holy guisarme. Even with your reduced casting ability, you can still do no-save, battlefield control, and buffing spells nearly as well as a straight-class caster and you can do multiple target save spells reasonably well as long as you pick your targets carefully.
Principle 4: Rely on your party. If you're the only arcane caster in the party, that's not necessarily a problem. The cleric or druid will have to pick up a bit in the blasting department but you can use battlefield control spells to maximize the advantages of your party makeup: more fighting power than most parties. (If you're an iconic fighter/wizard/cleric/rogue party (with the eldritch knight filling in for the wizard), for instance you can put everyone on the front lines instead of having a few party members playing defense and keeping the wizard out of harms way). Non-traditional parties can work quite well, but you need to adopt non-traditional tactics.
