Ask any Indianapolis print shop what causes the most reorders and exchanges on group jobs, and sizing miscommunication tops the list — well ahead of print quality issues.
Unisex sizing runs differently than people expect
Most blank apparel used for group orders is unisex-cut, which tends to run larger and boxier than women's fitted sizing that people may be used to shopping for personally. A "medium" in unisex isn't the same fit as a "medium" in a fitted women's tee — this alone causes a large share of sizing complaints.
Provide a real size chart, not just S-M-L-XL labels
Sizes alone don't tell people much. A chest-width or body-length measurement chart (which most shops or blank manufacturers can provide) lets people size against a shirt they already own rather than guessing based on their normal retail size.
Always order a size run buffer
For any group order, adding a couple of extra shirts in the most common sizes (usually M and L) is cheap insurance against a missed name on the list or a sizing mistake, especially once the order has already gone to print.
Youth vs. adult small is a frequent mix-up
Youth Small and Adult Small are meaningfully different sizes, and this distinction gets lost constantly on team and family orders spanning kids and adults. Make the youth/adult split explicit on any sizing form, not just implied by a size label.