Well, depending on what you use..Try to make your mouth close a bit more when your tokin so you take in less air/smoke at the same time, if you can kinda pinch your lips so its just a tiny hole, you can suck slower for longer. I find this really helps me when ripping a bong.
hit bongs everyday! when i smoked out of my roor everyday, i could down 2 packed bowls to myself in one sitting within no time at all.. so thats actually alot considering when i first got it 3 hits would leave my throat on fire. point here is that the more you smoke at once, the more you learn to tolerate the hits (i guess).
working out expands and strengthen your lungs. and it also depends on what strain the weed is. Bammer will have less THC crystals and be more dense leaf and will burn harsher (guessing that it's old and quite dry). Fresh, dank weed will be eayser to smoke because it goes down smooth alowin' you to take longer hits wile getting the same amount of smoke allowing you to get higher.
Just practice. Choke yourself to death with every single hit. Eventually you won't be able to make yourself cough anymore. NOTE: This method is very very expensive. You will end up smoking lots of weed by the time you are unable to cough.
im no fan of nictotine, but go buy a pack of cowboy killlers (Marlboro Reds) and smoke them they will be very harsh at first but then you will hit herb like a champ