Are you priming the engine?
An odd thing (seemingly odd now...) I see a lot of new guys do when attempting to start, is that they blip the throttle to WOT a couple of times, set the remote down, try to start it... repeat. I have explained to each and every one of them I encounter that blipping the throttle does nothing when the engine is off. They are under the mindset that these are like old carbureted 1:1 car engines that have an auxiliary mechanical pump that squirts fuel into the engine when you pump the gas before attempting to start. Problem is, they don't. So, you can pump the throttle as many times till your hearts content, it makes no difference. Fuel does not get "pumped" into the engine this way.
This is the sequence of events I use when starting a cold engine:
1) prime the carb first by detaching the pressure line off the pipe and blowing into it gently. I watch the fuel get pushed through the lines and I stop when the fuel reaches the carb.
2) Then I reattach the pressure line to the exhaust.
3) Put the heater on the plug, let it sit for about 5-10 seconds
4) Grab the remote, hold it at 1/4 throttle, try to start.
Typically my engines start on the 2nd/3rd pull.