What feats would you use to make a dragon character, you know the type... fly by burn stuff, swallow things, swooping intimidating awesome, needing some help with feats, advice?
Well if you want to use Flyby, you'd need the Flyby Attack monster feat (it's in the Bestiary, so you'd need GM permission to stick it on a PC. If you are the GM on the other hand, go crazy with it, I suppose).
Other than that, it sounds like what you want isn't going to come from feats so much as from classes. Look into the sorcerer's Draconic bloodline, and into the Dragon Disciple Prestige Class.
Any race that has an arcane spell-like ability can qualify for Dragon Disciple, but it works best with Magus.
Alternatively, a Synthesist Summoner using a Quadruped Eidolon with the evolutions Wings, Tail, Bite, Wing Slap, Breath Weapon, and Energy Resistance.
Sorry, I am the GM, but I am looking for feats at this point.
Are you adding classes to a dragon, or trying to replicate a dragon's abilities with another characters?
He will have caster support and a mounted cavalier on his back, I dont like the classes idea for a monster so other wise just feats.
Flyby attack, snatch (if large enough), wingover, imrove crits for claws and or bite, deafing crit, blinding crit, just a few for example.
All of these can add some nasty bonus to a dragon.
I didnt even think about the crit feats, nice!
So you are modifying a dragon to suit your story needs?
Since he's carrying a rider, and getting external spell assistance, I'd be looking for feats/abilities to maximize his attacks and mobility.
Flyby, wingover, weapon focus(bite or claw or both), hover, multiattack. All make sense. I'd be tempted to give it pounce.
yeah for flavor text for the deafening crit you could have the dragon Roar right before the strike.
And the blinding could be from the wings beating the air and blowing jagged debris into the pcs eyes.
I played and ran a few Council of Wryms games, some adapted for 3.0, and 3.5, and we had a lot of fun with tooling up dragons.
A Dragon Pc is fearsome. (in the proper setting of course.)
Is improved natural weapon worth while here?
I would apply it to claws for more mileage, pair that with improved crit and some other of the crit shenanigans at it should make it a nasty customer, but you want to make the fight memorable..not lethal. :)
Is there a way to give a monster pounce or is it just give it pounce cause I say so?
You are the GM. You are god. If you say that critter has pounce, then it now has pounce. ;)
Your the GM, you can do what you want, just give the players some visual clues, maybe the dragon is much quicker in its actions than usual, or is more heavily muscled than the norm, give them some lead in that this may not be a run of the mill dragon, plus if you have some insightful players they may alter their tactics just based on a good flavor description.
Are there spells other then polymorph effects that can give something burrowing or other movement types?
Blue dragons burrow.
Improved Maneuverability is a must at least one time, possibly more.
I love giving my dragons off levels of sorcerer to adjust their CR to the APL of my players, and usually go with the Arcane Bloodline, pick up a familiar for initiative, and have him take Improved Initiative as well.
Power Attack is always solid.
Look at Quicken SLA for those at will abilities.
3.5 had an entire splat book about optimizing dragons, the Draconomicon, there is some good stuff in there that is pretty much usable without having to do any adjustments to the feats. Metabreath feats are pretty cool.
Higher level dragons also have spellcasting, so some Metamagic feats are not bad ideas. If you get access to high enough level spells to quicken magic missles for added action economy, or Extend a Mage Armor for unpassable AC.
Dragons are the sickest BBEGs in the game, hence the namesake.