Look for a size that's just large enough to carry a hardcover book or a 7-inch tablet. That way you won't be tempted to overstuff the bag with "just in case" extras that will kill your shoulder after an hour's wear.
Clockwise from top left: Neon Yellow Crossbody, $65; RachelRoy.com. Tory Burch "Robinson - Mini" Crossbody Bag, $195; Nordstrom.com. Legacy Colorblock Leather Swingpack, $178; Coach.com. Colorblock Perforated Leather Mini Bag, $168; AnnTaylor.com. Ted Baker London Large Quilted Crossbody Bag, $165; Nordstrom.com.