Lots of threads on collimation - I suggest that you read up on these.
If you are currently doing nothing to collimate, a cheap laser collimator will make it better. As you will read, both a cheap laser and the technique it uses to align the primary mirror are less than perfect, but much better than doing nothing. And easy as well - in daylight or at night.
Here is a cheap one:-
"Guan Sheng deluxe Newtonian laser collimator" at Andrews Communications:-
http://www.andrewscom.com.au/site-section-10.htm