This tutorial will teach you how to create slick vector buttons that are easily scalable to any size. It's a simple matter of modifying gradients and applying a few effects. Created in Adobe Illustrator CS6.
1. Draw out the base shape
Create the vector buttons using a rounded rectangle drawn with the Rounded Rectangle tool. The dimensions I used are 200w x 50h with a corner radius of 5 px.
2. Add in some color
Apply a gradient to the shape. Here are the color values and position of the color stops I used. Set the gradient's angle to 90 degrees. Note that the second midpoint marker (the little diamonds above the gradient bar) is set to 25%. The others are left at 50%.
3. Here comes the highlight
To create the thin highlight on the button, make a copy of the shape and paste it (using Edit > Paste in Front) into a new layer above the original layer. Lock the original layer and select the copied shape. From the menu bar, choose Object > Path > Offset Path. Enter the values shown and click OK.
4. Delete the leftover
Delete the original shape to leave only the smaller shape and apply white to the shape.
5. Pathfinder power
Copy the smaller shape and use Edit > Paste in Front for precision pasting. With the copy selected, press the Down arrow key on your keyboard once. Select both shapes and apply the Minus Front command from the Pathfinder panel. Here's the end result.
6. Blending modes to the rescue
Select the new shape and select Soft Light from the Transparency panel.
7. Glossy reflection
In this same layer, create a short rectangle that matches the width of the highlight shape. Apply a white fill to the rectangle.
8. Transparent gradient
Apply a transparent to white gradient to the rectangle using the values shown.
9. Blur the gloss
Blur the rectangle using Effect > Blur > Gaussian Blur. A value of 5 for the radius is suitable. After completing this step, lock this layer.
10. Shadow the shape
Unlock the original layer and select the shape. Add a drop shadow (Effect > Stylize > Drop Shadow) to the shape using the values shown below. When complete, lock this layer and create a new layer above all others.
11. Add in the text
Time to add in the text to complete the button. For this button, I chose to go with Helvetica (surprise!) and a text weight of Medium Condensed. For those following anxiously along, set your font size to 30 px and the fill to white.
12. Drop shadow the text
Apply a drop shadow (again, Effect > Stylize > Drop Shadow) to the text using the values shown. Once you do that, you raise your hands in victory and, perhaps, do a little happy dance. That's what I'm doing right now.
If you want to save time creating other buttons, choose Align Center, via the Paragraph panel, to keep the label centered within the button's width.
One more thing:
To change the button's color, you simply edit the gradient. Take note that there's really only 3 colors used in the button. Two of the color stops are the same while the one at the bottom is a lighter shade of the light color used at the top of the bottom. With careful adjustment, you'll want to retain the highlight at the base of the button.