Kleud - 4:08 pm on Apr 15, 2010 (gmt 0)
1. I suppose, Google Adwords is sufficient when dealing with a few customers.
2. Have to agree on that one with AussieWebmaster - don't risk being left out.
3. Percentage is a good choice and most accurate in fact. (you can drop % a bit if campaign budget is big, say 5% of 1000 and 10% of 500 don't differ much, ha? :) )