Some general advice for all wizard PCs
1. Play an elf (preferably a grey elf for the INT bonus) and take the Generalist Wizardry racial substitution level from Races of the Wild. This gives you an extra learned spell every level and the ability to prepare one additional spell of your highest level every day. This synergizes with...
2. Take the Alacritous Cogitation feat from Complete Mage. Leave your bonus spell from Generalist Wizardry open and once a day you'll be able to cast ANY spell in you spellbook. This particular trick has saved my wizard's @$$ more times than I can count! This ability is what makes the automatic Scribe Scroll feat worthwhile- but AC works even better because it's much more versatile AND it doesn't cost you the gold and xp of scribing all those emergency scrolls. It's so much better in fact I would advise you to ask your DM if you can have AC in place of Scribe Scroll at 1st level. The ability to cast ANY spell in your spellbook, even just once a day, will come in handy more ways than you can think of. Speaking of spellbooks...
3. Take the Collegiate Wizard feat from Complete Arcane. Coupled with your elven wizardry you'll be adding FIVE spells to your spellbook every level! This should give you all the spells you'll ever need- and it will make the AC feat even better. If your DM allows flaws, consider taking one to get CW. Not having to rely on treasure drops to build an awesome spellbook will be worth it.
4. As suggested earlier, definitely take the Spontaneous Divination acf from Complete Champion. Now you never have to worry about preparing divinations. But the acf is even better than StreamOfTheSky implied in his post because it isn't limited to "any divination spell you know" (which implies only spells in your spellbook), the exact text says " You can spontaneously cast
any spell of the divination school by sacrificing a prepared spell of equal or greater level." That means any divination spell from any list- provided you have an appropriate level spell to sacrifice. The acf would be worth it even if it was limited to spells in your book, but as written it's not so it's gold.
Beyond that, any of the suggestions so far in the thread are great- my suggestions just adds to any of them- well, except for the specialization advice, obviously.
