To find the right engagement ring size, consider factors like the ring's width and potential finger fluctuations due to temperature and humidity. Seek advice from family or friends who know the recipient's size or use a plastic ring sizer or printable guide at home. Methods include measuring with string or paper and comparing it to a ring sizing chart. While these DIY methods can provide estimates, it's wise to confirm the size with a jeweler before purchasing. Reputable jewelers often offer free resizing services post-purchase for added convenience.