I've been playing one for the past 2 years in the RPGA's Living Greyhawk campaign. The key is finding synergy between your fighter and your wizard abilities. If you don't you're either a wizard with a lousy caster level or a fighter with lousy hit points and a pathetic BAB. If you can find your niche, however, you can create something effective.There are two basic types of fighter/wizard: the wizard with a little bit of fighter and the fighter with a little bit of wizard. Since I'm more familiar with the first, I'll discuss it first.
That niche has changed a lot between 3.0 and 3.5.
In 3.0, the niche was high AC.
Normal Armor+real shield+shield spell+dex+long term buffs+haste=very good AC.
Bull's Strength, Cat's Grace, Endurance, False Life, and Polymorph Self could be used to gain physical stats that were at least equal if not superior to the mundane fighter. Haste equalized attacks. Quickened spells or Spellsword channel (useful ability but whatever you do don't take more than two levels of the class) added to your damage potential.
In 3.5 it's much harder to get good AC so you'll have to focus on offense and on miss chances more.
Good spells:
Alter Self (AC boost)
Polymorph Self (physical stat boost, AC boost, size boost (important for tripping, etc)
False Life (hit point boost)
Heroism (medium duration buff helps with your BAB problem)
Mirror Image+blink have good synergy
Ray of Enfeeblement (yet another way to make yourself safer and your enemies more vulnerable to tripping).
There's good synergy between Blink or Improved Invisibility and Expert Tactician. There's marginal synergy between Power Attack and True Strike (better in 3.5 but still not that useful)
Stats: You'll want a good mix of physical stats and intelligence; but you can live with an intelligence as low as 13.
My recommendations on 28 point buy:
Str 14, Dex 14, Con 14, Int 15, Wis 10, Cha 8
or Str 15, Dex 14, Con 14, Int 14, Wis 10, Cha 8
With higher point buys, I'd increase intelligence first then con or strength.
Feats:
3.0 Extend Spell, Persistent Spell, Combat Reflexes, Expert Tactician
3.5 Quicken Spell (so you can cast and attack in the same round), Combat Reflexes (good in its own right since 3.5 combat is very focussed on reach), Expert Tactician, Combat Expertise, Improved Trip, Power Attack
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