I switched to vaping so didn't have any of the cravings or irritability.
You might find you cough more for a couple of weeks after you stop smoking. This is your lungs starting to work properly again and clearing all the clag.
Smoking masks gum disease by destroying your capillaries so as these start to grow back you might get bleeding gums.
You might get constipated. Strong coffee can help 
Some people get anxious or depressed but this is usually short term.
There are basically two ways of quitting - with nicotine (gum, patches, vape etc.) or without (cold turkey, Allen Carr etc.) and for best results, do one or the other, rather than a mix.
If you are not using nicotine then don't use any at all. It won't take the edge off it will put you back at square one. You need to just plough through. You might feel a bit shit for a few days but the strong cravings go very quickly and each craving only lasts a few minutes.
If you are using nicotine then don't skimp on it. Lots of people try to use the minimum they think they can manage on, and try to cut down too quickly. All this does is put you into a prolonged state of misery and craving so you're much more likely to relapse. The trick is to use enough, and for long enough, that you forget to smoke. Then you can cut down. You can double up on methods, e.g. a patch for slow release with a vape or a spray for a quick blast when needed.
There's also Champix which is a prescription drug. I've heard it's very effective but can have unpleasant side effects and is not recommended for people with a history of mental health issues.
Whatever method you use, you're likely to do better if you have support, either from friends and family, a thread on here or local stop smoking services.
No single method works for everyone so if one thing doesn't work then try another.
Good luck!