Second that, Not only respect other businesses but when I am working for one I am aware that every penny they pay me is a negative for their company. So I make sure my work is done as quickly as possible and I don't "milk the clock".

In my experience the worst clients you can spot right away. They are the ones who are trying to get a discount. The work is always too much and it is never good enough. I filter clients by letting them know costs in advance. If they complain or suggest that it is cheaper down the road I politely suggest they find someone else. Otherwise...you end up doing 2x the work for half the price.

Also, if someone advises you should "Do the work at a discount and then it will be good advertising for your company". I suggest either walking away immediately or asking exactly what type of "advertising" they are actually going to be doing. From my experience these people give the worst reviews.