No bookseller has to be reminded that a successful bookstore's profit margin is, more often than not, slim, and -- in the current economic climate -- possibly non-existent. It's for that very reason, said Michael Barnard of Rakestraw Books in Danville, California, that booksellers must be pro-active in how they handle credit cards and card transactions, to minimize the associated costs and risks. Barnard recently led a session on credit at the Northern California Independent Booksellers Association Trade Show.