Figure out which powers you want to use the most at a cosmic.
Find a/the toggled form that goes with these powers and triggers more stacks based on those powers. You may want to test this on the practice dummies to make sure it works the way you think it does.
Read in the description for which stat the damage scales with. This stat will be one of your super stats if not your primary super stat. Also, Make sure this is the kind of damage you want to do (ranged, melee).
Find at least one power that triggers stacks for your buff. Test it.
Find a power that provides a defense debuff for the type of damage you are doing.
Energy! Do you need a huge amount of power for your most amazing attacks? Do you just need some power at the beginning?
Need power for big attacks? You might need endurance as a super stat.
Need power for maintains? Consider intelligence for its cost reduction.
Need power at the start of a fight? Recovery might be something you need.
Make sure your powers trigger your energy unlocks. Also, you might get energy from your form when you get a stack. Some builds might not need END,REC, or INT as a superstat.
Note: Power conversion in Laser Sword works well with END
How do you do damage with this power?
Do you need Criticals? You probably want Dexterity as a super stat. Make sure your chance of making a critical is at least 30%. Also, your critical bonus should be pretty high.
Bleeds, Poisons, and other DOTS. Do you need to stack or modify what you are doing for more damage?
What conditions do you take advantage of when doing damage?
What categories of damage are you doing? Do you have a slotted passive that goes with this type of damage in a damage role?