Mechanics aren't too hard. 20 + the spells level + the feats level adjustment. The feats level adjustment doubles if you don't actually know the feat (you can use the spell to add feats without increasing the level of the spell).
You earn ranks at a rate of two skiil points per 1, modified by Int.
besides back lash, you lose access to a spell per day and spell known every 5 ranks. The first is from first level, the next is from second level, etc.
Backlash has a table, but you can DM that as needed.
Spontaneous casters can also use the skill to cast a spell using a lower level spell slot (can't adjust wit a feat). I don't remember the roll though.
If you want an official copy, get dragon magic from MGP. Evil stuff. Using the skill to improve spells, gain draconic features (sorcerers only), gain draconic spell like abilites (bards only), and new 'power word' spells requiring the skill. There's also the drocomancer (1oth level ability is to negate the penalties of the other abilities).