Because of the respec, I'm going to assume people will plan for some of that and base this strategy around picking powers someone might not normally go for.
Fire / Radiation
Pre 32
Fire Powers: Ring of Fire, Char, Fire Cages, Smoke, Flashfires, Cinders
Radiation Powers: Radiant Aura, Radiation Infection, Enervating Field, Accelerate Metabolism
Power Pools: Swift, Hurdle (or Health), Stamina, Hasten, Travel Power
Taking all the powers listed will put you at 26 or 28, depending on what Travel power you take. Slotting prior to respec/level 32 should include the following powers to be 6 slotted: Ring of Fire, Flashfires, Stamina, and Hasten (or 5 slots if you plan on using Accelerate Metabolism constantly). Beyond that, make sure you pay attention to Char, Fire Cages, Smoke, Cinders, and Accelerate Metabolism by giving them 3/4 slots. A lot of the powers you have at this point are one enhancement wonders, like Radiant Aura, Radiation Infection, Swift, Hurdle, and Enervating Field, so don't worry about them unless you're comfortable with your current enhancement layout.
When slotting enhancements, concentrate on accuracy in your hold powers, followed closely by duration. Third priority should be recharge, but Hasten should help a lot with that. Cinders should be used once you have it, in nearly every situation where there is a boss. Cinders followed by Char will overcome the magnitude (if Cinders didn't do it by itself) and hold the boss. This is pretty key for survival. Otherwise, the standard hold method for Fire Controllers is Flashfires + Fire Cages. Smoke should always be used before any AoE hold power.
Otherwise, because of the new mission bonuses, try to live off of story arcs and groups when you can. Your primary method of killing should be an AoE control power like Flashfires (followed by Fire Cages) or Cinders, while applying Ring of Fire and brawls to finish enemies off. Ring of Fire should go by the standard attack power formula of 1 accuracy and 5 damage enhancements.
Post 32, Ring of Fire will never be used, and should not be picked up when respecing. At this point, your control methods will remain the same, but you now have Imps to do your damage. Also, be sure to pick up Bonfire if you aren't going to get Group Fly. Casting a Bonfire below a flying mob will bring them to the ground into the range of your imps. At this point, most folks don't need a guide, as things become easier, so I won't bore you with what 1000 other people are going to tell you.
