yeah i recommend looking at the chainline the chain and the cogs should (pretty much) form a straight line front to back.

and big deviations to one side or another and you bike will have the tendnecy to throw a chain. on a fixed gear this is BAD.

chain tnesion is also tricky. if you have a good chainline you can let it go pretty loose... lots of people will tell you tight is good but too tight and your wearing your gears down prematurely. if it dosen't spin freely in the stand it is too tight.