Do yourself a BIG favor and get some silicone grease and lube up the inside of the new plug boots along with the other suggestions. I have also found it extremely usefull to use one of the old boots placed on the new plug to start it in the hole. This does two things for me. First is to give a better grip and secondly if the plug starts cross threaded it will slip and not damage the head and you get a second chance. Good luck.