There is a section in the back of the Advanced Race Guide for the creation of new races. You just need to come up with a set of abilities that match what the 4th Ed version gives you. I converted a "Draconic" character from 3.5 and I talked through what I got with the DM:
Humanoid (Draconic) 0pt
Size = Medium 0pt
Speed = normal 0pt
Ability = +2 stats x 2 2pt
Langauges = standard = 0pt
Immunities +4 vs Sleep and paralysis = 2pt
Natural Armour +1 = 2pt
Skill +2 intimidate and Perception = 4pt
2 Claw attacks (d4) = 2pt
Lowlight / Darknvision = 3 pts
Total = 15pts which was a little high but the DM was happy enough.
Generally just allowing a player to min/max with his class is bad idea, but working together to come up with something generic is good.