There are a lot of practices and most of them require handling with care your Email List and your Template. And the most important is the IP reputation which it affects where the email lands. I recommend the warm-up procedure from time to time since it can really be the most important when your emails don't land where they should. At ZeroBounce there is also the Inbox Tester which can be a nice test for your Template to see where it lands. As a conclusion, don't overlook the IP reputation and warm-up the IP from time to time and also be very cautious with the words in the Email Template. Hope this helps!