I'm the self proclaimed king of nitro consistency. Ask the guys at this years ECB.

My tips for good running nitro engines in random order. I follow all of these myself.
1) Get rid of the stock fuel line and get the proper lengths of good line by GS, etc.
2) Use a fuel filter and clean it periodically
3) Use a fuel tank without a primer if possible (air leaks)
4) Make sure the engine is sealed properly (RTV) and head bolts tight
5) Clean your one way bearing periodically
6) Ditch the stock air filter and get a good one like the Motorsavers. Keep it clean!
7) Use the right glow plug for your engine / nitro % / ambient temp
8) Use good quality fuel. Keep the container sealed.
9) Don't leave any fuel in the tank at the end of the day. Start the engine to clean out the fuel in the lines
10) Use after run oil - just a few drops down the carb
11) Keep a few well charged glow ignitor batts, or get a 1.5V hobby battery and glow ignitor (best setup IMO)
12) RTFM when it comes to break-in and base needle setups!!
13) Adjust the needles 1/8 of a turn at a time and run for 2 min before re-tuning. If you fubar them go back to break-in settings and start over.
14) Temp guns / monitors - get one!!
15) Blue smoke = Goooood, No smoke = baaaaad
This sounds like a lot, but you need to do it if you want to run Nitros.