Whenever we had a new customer, someone we didn't know etc. When buying fish we asked what the fish were going into, with... If it was for a new tank, we would only sell a couple, we had a wall chart with the cycle on it. Got the customer in each week for the next 4 weeks for free water tests. That way week 2 & 3 they might buy plants, ornaments etc. week 4 buy a couple more fish, week 5 if still fine, buy what they like....
That way too we can spoon feed, littles bits of info each week. End up with a happy, regular customer who recommends you to others. 8)
Frenchy