Initially, just dig in, explore and choose or do whatever looks interesting. The game is awesome once you get to grips with all its features. Your very first character will normally be a royal cock up eventually as you will tend to try to assign points into every available skill. NOTE: This is NOT a bad thing and is encouraged for new players. By all means - try all the available skills of the classes. You can always respec later in game to tune for the skills and synergies that you will start to see viable once you start picking up certain gear and set pieces.
There is no wrong path here and you will get much more enjoyment and achievement by following your own gut instinct. You can definitely look at forum builds and guides for later end game and performance, but trust me, there is no better feeling than finishing the first level act with your own home grown character which you have scoured and explored every last inch of the maps.
Welcome to the Dawn.