This tutorial explains how to create something like the Aqua button used on Apple's web site. It's not an exact replica since it would take a lot more steps to reproduce Apple's version. Instead, this tutorial shows the basic steps behind the technique used to create a smaller-sized Aqua button . It doesn't work very well for big buttons.
Don't be scared by the number of steps. The tutorial itself is very simple.
Create a new channel². Using the Elliptical Marquee¹ tool, make a circle selection. The selection height will define the height of the button. Using the Paint Bucket¹ tool, fill the selection with white.
Using the Rectangular Marquee¹ tool, select one half of the circle. Reset the colors (press 'D'). While holding the Ctrl key drag the selection to the right (or left, depending on which side you selected).
Using the Rectangular Marquee¹ tool, select the empty area between circle halfs. Fill the selection with white using the Paint Bucket¹ tool.
This is the shape of the button.
Load selection² from the channel. Create a new layer and fill the selection with R: 104; G: 147; B: 255; HEX: 6893FF; using the Paint Bucket¹ tool.
Apply the Drop Shadow layer effect (Layer > Effects > Drop Shadow) as shown in the picture. Use the R: 66; G: 99; B: 188; HEX: 4263BC; color.
Apply the Inner Shadow layer effect (Layer > Effects > Inner Shadow) as shown in the picture.
Apply the Inner Glow layer effect (Layer > Effects > Inner Glow) as shown in the picture.
Create a new layer and group² it with the button layer.
Load selection² from the channel created previously. In the main menu select Select > Modify > Contract. Set the contract value to 3 (or approximately 10% of the button height). Create a new channel² and using the Paint Bucket¹ tool fill, the selection with white.
In the menu bar select Select > Feather and set the Radius value to 3 (or bigger if you are making a bigger button). Reset and reverse the colors (press 'D' then 'X'). Using the Linear Gradient¹ tool make a gradient from the bottom of the selection to the middle.
Keep the selection active
Set Blending Mode to Screen and Opacity to 60%. Duplicate² this layer and group² it with the others. Set Blending Mode of the copy to Color Dodge and its Opacity to 25%.
Create a new layer and group² it with the others. Reset colors (press 'D'). Using the Linear Gradient¹ tool make a gradient from the top of the selection to the middle. Set the Blending Mode to Multiply and Opacity to 20%.
Load selection² from the channel created in step 9 (the one which is contracted by 3). Using the Rectangular Marquee¹ tool subtract² the bottom part selection as shown in the picture. Create a new channel² and fill the selection with white using the Paint Bucket¹ tool.
Apply Gaussian Blur filter (Filter > Blur > Gaussian Blur). Set the Radius value to 4 and press OK.
In the menu bar select Edit > Adjust > Levels. Set the Input Levels to 120, 1, 130 and press OK.
Create a new layer and fill the selection with white using the Paint Bucket¹ tool. Set Blending Mode to Overlay.
Add mask² to the current layer. Make a selection as shown in the picture using the Rectangular Marquee¹ tool. Reset colors (press 'D') and using the Linear Gradient¹ tool make a gradient on the mask from the bottom side of the selection to the top side.
Done!