This is the easiest method for slicing images. The New Layer Based Slice command will create a sliced based on what is visible in the chosen layer. It also allows for effects like drop-shadow.
open index.psd in photoshop
select the layer you want to create the slice from
go to Layer>New Layer Based Slice
select the slice select tool
double-click the new slice
in the Slice Options box, give the slice a short descriptive name (NO caps or spaces...this will be a file name!)
click OK
repeat for additional slices you would like to create