Foster practiced mostly corporate law, eventually earning nearly $300,000 a year. Known for his extensive preparation of cases ahead of time, including the creation of decision trees, Foster developed a reputation as one of the best trial litigators in Arkansas. Hillary Clinton's memoir calls Foster "one of the best lawyers I've ever known," and compared him in style and substance to Gregory Peck's portrayal of Atticus Finch in the classic 1962 film To Kill a Mockingbird. In Bill Clinton's memoir, he characterizes Foster as "a tall, handsome, wise, good man." Writer Carl Bernstein has described Foster as "tall, with impeccable manners and a formal mien ... elegant in perfectly tailored suits, and soft-spoken to the point of taciturnity." Writer Dan Moldea characterized him as "a 'can-do' Lawyer who worked best when under pressure." Phillip Carroll, the leading litigator at Rose Law Firm, once said of Foster, "He was my ideal of a young Lawyer." The ABA Journal reported that Foster was "acknowledged by many as the soul of the firm".