wizard working towards a lich

[mananimal]

How would one start out and which books should I look in?

The more suggestions and idea the better.

If anyone has done this before can I see what they did to start out?

[Helic]

Read the entry on "Lich" in the Bestiary. Expect to spend hundreds of thousands of gold and survive many deadly, deadly adventures over the course of decades. Be prepared for difficult skill checks (probably in Knowledge: Arcana and Knowledge:Religion, which covers undead), probably in the DC30 range. Every lich's journey is unique, and probably tailored to his background, including:

Horoscope (consult with distant star-gazing temples - do jobs for them so they'll give you the right starcharts, or just kill them and take them)
Lineage (track down your ancestry as far as possible. Then probably kill them all to fuel your final rituals)
Likes (abandon/destroy everything you hold dear in pursuit of immortality)
Religion (abandon your former gods, call upon the dark ones to validate your quest, that'll get messy fast)

You get the idea. Becoming an undead abomination should not be for the faint of heart (or even the evil, but instead the EVIL).

[Drachasor]

I'd rather put my consciousness in a construct, personally. You can get halfway there with Magic Jar.

Also a fun idea: Sentient Demi-plane. Would want to build up a very large and nice demiplane first. Also, need minions (simulacrum, constructs, etc). No remotely clear way about going about this in the rules, however. Also, I think technically Disjunction might really hurt, unfortunately. Maybe a Wish could be used to make it undispellable.

Or becoming a planet is good. That's really just a very large construct. It is hard to kill a planet. And whether you go Cybertron or Gaia, plenty of people to be friends with, respect you, and help you out.

Becoming a lich though? Kind of lame, imho. Undead are not cool.