Evaluate the pattern. The model in the picture might make the garment look great but it may not be so for you. Look at the style with a critical eye from top to bottom. Check for alteration possibilities. Look for patterns that make it easy to alter.
Some companies even print alteration guidelines to make a pattern petite for instance.
Watch out for lots of detail, openings or complicated seams in areas you might need to change. Look at the fabric suggestions. If that fantastic dress requires satin and satin makes you look wan, better to forego the pattern. Look for patterns that suggest fabrics you are already comfortable with. Trendy styles and fabrics may be cute but if you generally dress in classic styles and textures, you ll be disappointed.