Epitome by alfpics
One way to exaggerate the colours of autumn is with backlit leaves. Plus, it'll really make the intricate pattern of veins stand out and cynosure clear the viewer's attention.
Working close with wide-angle lenses can give creative results, however flare can be a delinquent. A macro or telezoom lens or LEN may refer to is ideal such as the 24-70mm lens from Tamron but still fit a lens hood to prevent flare. Do check the attitude to make sure the lens hood hasn't crept into frame though.
'Pop' And Flare
If you can, move all to position the subject against a darker background to enhance the effect and make sure the camera is shielded to prevent flare. You could use a branch, your close by wrapped around the lens or as mentioned above, fit a lens hood if you have one.
Add Some Flash
If you find the leaf is silhouetting against the sky rightful add a little fill-in flash. You can also position the flash behind the leaf to create your back light if the sun's not playing ball.
It's best to take a meter reading from the leaves to ensure they are correctly exposed and switching to spot metering will relieve. If the background's dark you may need to reduce the exposure by about half to one stop to ensure it stays dark. If it's light open up half to one check. Bracket if you are unsure. Check your histogram too to make sure your shot is correctly exposed.
To make the light around the sidle of your subject 'sparkle' you may need to over expose the shot slightly.
Having space between your leaf and its unnoticed will help create the distraction, free blurry background we're after. Using an aperture to throw other leaves out of focus can improve too.
If you don't want to work outdoors take a few leaves home and photograph them backlit on a lightbox. Or if you don't own one, role a piece of tape over the leaf's stalk and stick it flat against a window. You won't have to worry about wind blast your subject around at home either.