You want to make sure you use very ripe bananas. Bananas that have lots of black specks. The blacker the banana is the sweeter it will be. I actually like to freeze my bananas when they have gotten too ripe to use later for banana bread. If you use frozen bananas, then let the bananas thaw before using them. Mash your bananas before adding them to the mixing bowl. I do this by hand with a fork since I have used frozen bananas they are very easily mashed. You could also use a pastry blender, potato masher, or a hand mixer. When you add the oil into your the sugar and eggs you want to S-L-O-W-L-Y add it in with your mixer on low. This step should take about a minute. So slow. If you add the oil in all at once you risk of deflating all that air you incorporated into the eggs and sugar in the step before. Measure your flour accurately. I use the spoon and level method. You can learn how to measure your flour in this post. Careful to not over mix. I like to use a spatula and fold in the dry ingredients by hand. You want to stop mixing once they have been incorporated. Too much mixing = too much gluten forming. Gluten is what will give a bread its chew, but for a banana bread you want less gluten to form. So we can accomplish that by making sure we don't overmix!