This tutorial is a very close replica of the famous Aqua button. It's not recommended for novice Photoshop users because it doesn't explain how to make each and every single detail.
This is an adaptation for Photoshop 6.
On a new layer create a pattern as show in the picture. Use 10-15% layer Opacity.
On a new channel create a pill-shaped button. In order to complete this tutorial, the pill must be 311x96 pixels in size.
Load selection² from the pill channel. Create a new layer and fill the selection with R: 65; G: 113; B: 166; HEX: 4171A6; using the Paint Bucket¹ tool.
Apply Inner Shadow (Layer > Layer Style > Inner Shadow) layer style to the pill layer as shown in the picture.
Apply Bevel and Emboss (Layer > Layer Style > Bevel and Emboss) layer style to the pill layer as shown in the picture.
Apply Satin (Layer > Layer Style > Satin) layer style to the pill layer as shown in the picture.
Apply Gradient Overlay (Layer > Layer Style > Gradient Overlay) layer style to the pill layer as shown in the picture.
Load selection² from the pill channel again. Contract selection (Select > Modify > Contract) by 10 pixels twice. Feather selection (Select > Feather) by 10 pixles.
Alt click the New Layer button at the bottom of the Layers palette. Create a new Color Dodge layer with color-dodge-neutral black color. Fill the selection with white using the Paint Bucket¹ tool.
Set the Fill Opacity value of the layer to 35% (equivalent of 35% transparency in PS5).
Apply Gaussian Blue (Filter > Blur > Gaussian Blur) filter with Radius value set to 10 pixels.
Load selection² from the pill channel and click the New Layer Mask button at the bottom of the Layers palette.
Select the pill layer and add mask² to it. Repeat step 9. Having the pill's mask active, fill the selection with R: 166; G: 166; B: 166; HEX: A6A6A6; using the Paint Bucket.
Apply the Gaussian Blur filter (Filters > Blur > Gaussian Blur) to the layer's mask. Use a value of 20 pixels.
Using the Rectangular Marquee¹ make a rectangualr selection as shown in the picture.
Create a new channel² and fill the selection with white using the Paint Bucket¹ tool. Skew (Edit > Transform > Skew) the selection as shown in the picture (hold Ctrl+Shift+Alt to achieve symmetry transformation).
Apply Gaussian Blur (Filter > Blur > Gaussian Blur) filter with Radius value of 10 pixel.
In select Image > Adjust > Levels. Set the Input levels values to 120, 1, 132 and press OK. Load selection² from the result channel.
Create a new layer. Reset colors to black and white (press 'D'). Using the Linear Gradient tool, make a gradient from the bottom of the selection to the top. Set Blending Mode to Screen and Opacity to 65%.
Add a text label, shadow and you have yourself a very nice Aqua button.