You may choose to take your average hit dice. Max hit die at first level, half max on even levels, half max +1 on odd levels.
If you choose to roll your hit dice and your max health is more than a full hit die (6 for 1/2-bab classes, 8 for 3/4-bab, 10 for full-bab, 12 for barbarians) under average when you level up, you may take the average roll if you roll under average.

Don’t forget about your favored class benefits. Choose one base class (not prestige) to be your favored class, and every time you level in that class you gain either +1 hp or +1 skill point. There are other options available to kobolds per class.

At 5th level you have 3 feats and +1 to any ability score after point-buy.

Kobold Race Page

On the kobold monster listing is a section from Classic Monsters Revisited, describing bonuses based on scale color. Do not allow this to influence your decision on scale color. You may choose any of the options below to apply to your character instead.

Additional +4 racial bonus to Stealth checks.

+4 racial bonus on swim checks.

+1 inherent bonus to one mental ability score (INT, WIS, or CHA).

+1 to the DC of any spell you cast with a chosen energy subtype.

+2 on saves made against fear effects.

Draconic Rite of Passage

Players may choose to have completed the Draconic Rite of Passage prior to gamestart. If you choose not to but decide later on in the game to do so, you must undergo the rite in-game.

A Kobold who undergoes this rite must first endure nine days of fasting. Immediately thereafter, the kobold must succeed on a DC 10 Concentration check to enter a deep trance that lasts for 24 hours. If the check fails, the rite must begin anew.
This rite requires sacrificing a gem of at least 100 gp in value. The kobold also permanently loses 1 hit point upon completion of the rite.

Upon completing this rite, a kobold chooses any 1st-level sorcerer spell. He can now use that spell once per day as a spell-like ability, using his character level as his caster level.
Each day, a kobold must complete the Searching for the Dragon meditation in order to recharge this spell-like ability for the day.