If you use a tensioner, use one that pushes up instead of pulling the chain down. Dynamic tensioners tend to do a better job than a static tensioner because your chain will stretch faster on a SS. Be sure that whatever cog you use, it is quality. It should not be the same thickness all the way across, rather fatter at the center to prevent the cog from trying to slice into the hub's cassette mounting surface.
Check this link out for proper chainline adjustment: http://www.sheldonbrown.com/chainline.html.
You MUST measure chainline unless you like headaches. Eyeballing a chainline will lead to more chain jumps which requires more tension to prevent which wears the chain faster...unless you are a lucky eyeballer. A dialed (+/- a mm or so) chainline with SS specific ring/cog will allow you to run a free-spinning chain tension without risking chain jump.
Once you take the measurements, how you space the cog on the hub is up to you. You can spend money on some blingy spacers or you can simply measure/cut 1.25" PVC. $45 for a SS chain ring, $30 for a cog, $2 for a 1' PVC or someone might have some laying around.