My go to technique
In Av or A for Nikon the camera will decide the shutter speed therefore if you focus and meter on the leaves which are bright the darker ares are going to go very dark due to the fast shutter speed, which is great if that is what you want. If you focus on the dark the leaves will be almost white and the dark will be a nasty grey ish.
So, if you focus on the leaves and lets say you get 1/200 and you move the camera to frame the shot, what happens? The shutter speed changes because the camera senses different light, maybe to 1/30 So what do you do?
You focus and meter on the leaves area and then you press AE button and then the exposure wont change even if you refocus!! How cools is that!!! You can adjust how long the exposure wont change for in settings or you can go to your manual and check out the AE button on your camera.
Also when the exposure is locked, you can actually manually adjust the exposure compenstation to make it darker or lighter as well!!
Have a go!