First, you have to check the sound quality of the banjo by playing it. If it feels hard to put your fingers around the neck and reach over the fingerboard, it may not be made of good quality materials. Check the strings to see if they are easy to press. Sometimes, the design of the banjo can look glossy but it might not be produced of higher quality materials. Most high-quality banjos have a thick neck so make sure to check that out as well.