One of the major gripes from fans heading into Diablo 3 was the apparent lack of customization.
At first glance, it looks like Blizzard almost dumbed down Diablo 3, simplifying it so much that it only lets you slot certain skills into certain hotkeys. The major problem with the current setup is that it doesn't allow much room for creativity. On my Demon Hunter, for instance, I can equip my primary skill on left click (to regenerate Hatred). On my right click is my secondary ability which uses the Hatred. Two of my Action Bar skills are reserved for Defensive skills, another for Devices, and another for Archery.
Are there plenty of combinations with this format? Certainly, but for an advanced Diablo player, it's somewhat limiting. Enter Diablo 3's "Elective Mode".
Elective Mode is hidden in-game under the "Options" menu. You can find it in the "Gameplay" tab under the "Interface" bar. What does this elusive mode allow you to do?
Once you've turned it on, you can assign ANY skill you've learned to almost any button, even if you've already equipped other skills from that category. It no longer restricts you into placing certain skills into certain hotkeys, enabling you to make whatever combination you want. For instance, with my Demon Hunter, I dropped all of my Defensive abilities for additional attacks. I now have two abilities to generate Hatred (Primary skills) and another two which use Hatred (Secondary skills).
If you still don't get it, I can now equip Hungering Arrow and Bola Shot (both from the Primary skills category) as well as Rapid Fire and Chakram (both from the Secondary skills category). The result is I don't have as much escape ability, but I dish out some major damage! Using Elective Mode I was finally able to customize my character to fit my playstyle! Freedom in Diablo 3 at last!
Assuming this isn't your first go around with Diablo, I highly suggest enabling Elective Mode immediately. It completely transforms the way Diablo 3 plays. Using Elective Mode I am now free to experiment with the builds I want. THIS is the way Diablo 3 should be played.