Do you find playing the piano easy? (Some classes take an inordinate amount of finesse to play right and its further frustrated by lag)
If you are brand new just try out the classes that grab your attention.
Otherwise choose a class that you feel you can play fluidly and more importantly, have fun with
Linked some things below that helped mehttps://metabattle.com/wiki/MetaBattle_Wiki
Collection of current builds that are in use separated by game typehttp://en.gw2skills.net/editor/
This build editor can be a good resource for trying out ideas, when you get familiar with traits, and mechanics
Can be a lag time when it gets updated though if there were recent balance patches. ( 1 minor one incoming afaik )