Let's look at the 3.5 Player's Handbook to see what they say about how sorcerers cast their spells:
Sorcerers create magic the way a poet creates poems, with inborn talent honed by practice. They have no books, no mentors, no theories--just raw power that they direct at will. Some sorcerers claim that the blood of dragons courses through their veins....In essence, the sorcerer is born with an innate gift at manipulating magical energy and basically trains himself (or herself) to use it. Makes sense. And since spellcasting is a complex and formulaic process, the sorcerer is probably going to have access to much more raw and unrefined ways to use magic.
The typical sorcerer adventures in order to improve his abilities. Only by testing his limits can he surpass them. A sorcerer's power is inborn--part of his soul. Developing this power is a quest in itself for many sorcerers, regardless of how they wish to use their power....
Sorcerers cast spells through innate power rather than through careful training and study. Their magic is intuitive rather than logical. Sorcerers know fewer spells than wizards do and acquire powerful spells more slowly than wizards, but they can cast spells more often and have no need to select and prepare their spells ahead of time. Sorcerers do not specialize in certain schools of magic the way wizards sometimes do. --PHB, pgs 51-52.
At first blush, you'd expect them to work something like the wielders of the One Power in the D20 Wheel of Time game. They can channel weaves of the One Power, which are tied to the four different elements and a fifth element of spirit. There are lots of weaves, but none of them are very detail-oriented or complex. In other words, complicated effects like for Leomund's tiny hut or contingency are non-existent. A channeler of the One Power can, perhaps, open a lock or make something float, throw fireballs or call lightning, or even effect the weather, but they can't do anything extremely specific, highly detailed, or complicated. They can't produce the effect of Evard's black tentacles, they can't change their physical forms, they can't summon demons or create undead, they can't inscribe glyphs that cause sleep, and they can't pass through wood or stone walls.
But they can still do some pretty heavy damage at early levels.
Now, this is what frustrates me about the sorcerer. For someone who uses innate powers, what the heck is he doing casting spells? Oh, he doesn't have to prepare them like a wizard, fine, and heck he can even forget about materials, but he still has the verbal and somatic components. In effect, he's a wizard who just doesn't forget the spells. Which makes no sense. To top it off, for all his inborn abilities, a sorcerer can pick a dozen-and-one spells that have no real relation to one another. There is no concept of a sorcerer who is primarily a fire-wielder while another has an affinity for sound and illusion while a third figured out how to manipulate space-time and open planar gateways. That's like having the inborn ability to dribble a basketball, hit a home run, and slapshot a puck, but not be able to play soccer, baseball, or basketball because one lacks the required skills. Either his abilities are inborn or he learns spells he doesn't forget. Which is it?
This is called fence sitting.
Well, Pathfinder fixed some of that by creating bloodlines. But they didn't fix it far enough. The sorcerer still has access to the same spells as a wizard, but now gets a whole plethora of bonus abilities for having a bloodline.
So I took matters into my own hands. For two weeks I went through all of the spells in the PHB until I had divvied them up among all of the bloodlines that Pathfinder offered. But it wasn't really enough. So I opened the Spell Compendium and went through it, padding out each bloodline until I was satisfied.
So, now each bloodline has its own powers but a very limited spell-pool from which the sorcerer can learn spells. In addition, the sorcerer only gets a familiar if he picks the single bloodline that offers one. However, the sorcerer has access to spells from outside the PHB and each bloodline has special powers and spells that are specific to that bloodline. I kept the bloodline powers the same as Pathfinder's, by-and-large. The only thing I changed was the specific spells the sorcerer has access to. I think this has balanced out the sorcerer pretty well and makes the class make much more sense.
For example, for the Draconic bloodlines, the sorcerer has to pick a dragon color and he gets some abilities and spells that are specific to that color. Why should someone with red dragon blood cast cold or acid spells? The red-dragon-bloodline focuses on fire spells. In addition, he gets a bunch of spells universal to all draconic bloodlines (regardless of color) that help him hide and protect treasure, armor himself, and fly.
On the other hand, someone with the Fey bloodline gets mostly spells that enchant opponents, hide themselves, or create illusions. The Infernal bloodline acquires spells that seduce and dominate others, get others to do their dirty work, and trap souls. Celestial bloodlines get spells that inspire bravery, banish evil creatures, create light, ward and protect.
Here's a sample to illustrate what I mean. You can use either the Pathfinder rules, Monte Cook's variant sorcerer, or the 3.5 standard sorcerer, just so long as you use the bloodline specifically for spells and special abilities:
Let's take a look at a different bloodline, the Aberrant:
The Arcane bloodline focuses on the raw manipulation of magical power to solve problems, defend yourself from harm, create and remove barriers, build and repair constructs, manipulate words and symbols, use telekinesis, and discern the innate workings of magical objects and spells.
0-level (Cantrips): Amanuensis*, Arcane Mark, Detect Magic, Launch Bolt*, Launch Item*, Mage Hand, Mending, Open/Close, Prestidigitation, Read Magic, Repair Minor Damage*
1st-level: Alarm, Animate Rope, Familiar Pocket*, Dispel Ward*, Erase, Hold Portal, Identify, Instant Search*, Mage Hand (Greater)*, Mage Armor, Magic Missile, Magic Weapon, Nystul’s Magic Aura, Protection from Chaos/Evil/Good/Law, Repair Light Damage*, Sleep, Spell Flower*, Tenser’s Floating Disk, Unseen Servant, Weapon Shift*
2nd-level: Arcane Lock, Augment Familiar*, Blast of Force*, Cloak Pool*, Continual Flame, Create Magic Tatoo*, Force Ladder*, Invisibility, Knock, Levitate, Magic Mouth, Quick Potion*, Repair Moderate Damage*, Resist Energy, See Invisibility, Rope Trick, Slapping Hand*, Sonic Weapon*, Speak to Allies*, Tasha’s Hideous Laughter, Web, Wraithstrike*
*This spell is found in the 3.5 Spell Compendium.
The Aberrant bloodline is alien. Spells focus primarily on warping and bending space-time reality in uncanny and strange ways, seeing the unseen, physical mutation, contact and communication beyond this dimension, sanity, thought-waves, and altering intelligence or knowledge.
0-level (Cantrips): Acid Splash, Arcane Mark, Prestidigitation, Read Magic, Stick*
1st-level: Animate Rope, Babau Slime*, Benign Transposition*, Cause Fear, Comprehend Languages, Cutting Hand*, Enlarge Person, Grease, Horrible Taste*, Jump, Reduce Person, Slide
2nd-level: Alter Self, Baleful Transposition*, Bear’s Endurance, Belker Claws*, Bristle*, Bull’s Strength, Chant of Eyes*, Detect Thoughts, Discolor Pool*, Discern Shapechanger*, Dissonant Chant*, Extend Tentacles*, Fearsome Grapple*, Fox’s Cunning, Fuse Arms*, Inky Cloud*, Malevolent Miasma*, Melf’s Acid Arrow, Slide (Greater)*, Ray of Stupidity*, Razorfangs*, Rope Trick, See Invisibility, Scare, Spider Climb, Touch of Idiocy, Web
That should illustrate my point pretty well. We can see where some of this is going--the bloodlines definitely have access to very different spells. This can make for interesting roleplaying, especially if there are two different sorcerers or a sorcerer and a wizard in a party. I mean, we all know sorcerers are essentially 3rd edition's boomstick.
Wait, before you go off saying that I just nerfed the sorcerer, remember he gets all of the special features from his bloodline that Pathfinder offers. For example, the Arcane gets a familiar, at third level casts metamagic spells at one slot cheaper, and keeps getting interesting stuff. The Aberrant gets a free acid attack that he can use at any time he wants, but gradually develops more and more physical traits that help with combat. I didn't nerf the sorcerer, I streamlined it and made its magical abilities make sense.