First you need a nice wildlife picture to add your dew to, I chose this nice flower, you can use whatever you like

Find a nice petal or leaf that you would like to drip your drop on, and use your circular selection tool, while holding shift, to choose a nice drip-size area.

Create a new layer, and use your gradient tool to fill your new selection with a black and white fade. Make sure the darker area is towards the top. Call this layer "light"

Create a new layer below your gradient layer, call this layer "shadow" Using the same selection from your gradient, fill it will black. If you lost your selection, ctrl click your "light" layer. Once you have filled it, go to Filter > Blur > Gaussian Blur. Depending on the size of your drip you can adjust your blurriness I used "4"

Now that we have created a shadow and a gradient, we need to turn this thing into a drip! Go back to your light layer, and change the layer mode to "overlay." Ctrl click your light layer again to get your original selection, and click back to your shadow layer. Press the delete key and you should have something like the picture below.

Now its time to add some shine

On your color palette, make your foreground color white. Then click the gradient tool, and change the gradient mode to "Foreground to Transparent." This option is towards the top of your screen.

Create a new layer, call it "shine." Make a smaller circle selection towards whatever side of the drop you want the light to be coming from, and fill it with the gradient.

You should have something similar to the picture above. Now we are going to simulate the magnifying effects of a water droplet. Navigate back to your original picture layer, and Ctrl click your "light" layer again to get your original selection. While on your picture layer, choose Filter > Distort > Spherize. And choose 100%

You should have a decent droplet going by now, here is what mine looks like:

Mmmm dew.