I want to include lemon/lime "slices on a fondant -covered wedding cake. What techniques for making real-looking citrus slices?

In my "Lemon Pie" cake I made the lemon slices by making a cane (sp) as you would when working with polymer clay. You could probably find a video on youtube showing you how.

Link on youtube

did you use fondant? how did you make it shiny?

I used gumpaste and to make it shiney I used a recipe on here for edible varnish. Lately I have used someone elses recipe that is corn syrup and alcohol mixed to make things look glossy.