i7 runs hot, and it doesn't take long before your stock cooler will be overwhelmed. The best first step comes b4 you even start to overclock, and that is to buy yourself a good aftermarket cooler like the Thermalright Ultra 120 Extreme or Prolimatech Megahalems.
How familiar are you with that board's BIOS?
Here's a few links for your reference:
http://i4memory.com/wp/article/327
http://www.techspot.com/review/129-asus-p6t-deluxe/page4.html
Or just type P6T-Deluxe BIOS into google and take your pick.
I have personally owned and overclocked that same combination with both D0 and C0 CPU's and it's dead simple to do.
Put simply, to get to 3.4GHz you shouldn't have to do much more than raise your QPI Frequency(bclock) and or CPU Multiplier (200MHz x 17 or 170MHz x 20).
Personally, I like to manually set the RAM timings (should be on the sticker on the RAM) and command rate(2T is good), and also to manually lock in the DRAM, QPI and CPU Multipliers.
B4 you go changing any of these settings though, ask yourself whether you want to leave your CPU power saving features on or off. I leave mine off all the time, but for you it would be a good idea to go to he CPU features tab in BIOS and turn off C1E, EIST, Virtualization. This helps with stability while overclocking and heat testing, as it keeps your CPU at a constant Multiplier and therefore frequency.
The other setting in CPU Features is Hyperthreading (HT) which you can leave on or turn off. If you are trying to get to 3.4GHz with a stock cooler, you might want to try shutting it off as it will cut down a bit on the heat produced by the CPU.
After you are done heat testing and stability testing(
Prime95 small/large ffts) your new overclock, you can try turning these features back on and see how things perform.
Not an exhaustive tutorial, but it should get you started.
