I think having my two daughters helped me the most. They were my guinea pigs. If they wore something a bunch and it fell apart (my baby pulled my first korker apart during lunch one day - after that, I always sewed my korkers!!), then I altered and improved the accessory. If you don't have little ones to try your items out on, then I'd ask a good friend or family member. See if they would be willing to test out some items for you and give you detailed feedback on how things held up, if they have suggestions, etc.
And practice, practice and before you know it, you won't have any glue showing, crooked bows, etc. You'll be a pro!