I would start by gathering info on the lore and the classes available or changes that have been made on them.For vanguard the Druid and Bloodmage(lBM will spoil the day
) seems the most interesting to play.
I always choose class first then the Race according to my class and lore but my favorite classes are Clerics,Shamans,Druids and monks.If I choose Cleric the Race will be (Human,Elf,Half-elf,High Elf,halfling).Shamans will be Dark elf,Orcs,human.Druids will be Orcs,Human,Wood elf and so on.But vanguard the choice is little more complex as there are more interesting Race.