This series of articles is a big help in understanding how to get the best out of Slic3r:

http://richrap.blogspot.com.au/2012/...tings-and.html

http://richrap.blogspot.com.au/2012/...ament-and.html

http://richrap.blogspot.com.au/2012/...w-can-you.html

Old Man Emu