It is better to give 100% attention to the task at hand, complete it, and move on to the next task rather than try to juggle multiple tasks at once. Eliminate as many distractions as possible, concentrate on a listing, and your productivity will dramatically improve because you will be focused.

Time blocking is dedicating a chunk of time to accomplishing one task in order to increase focus and productivity. For example, in the eBay world, you could dedicate 10 a.m. to noon every day to taking photos. Or 8 p.m. to 10 p.m. for listing. You may also choose to base it on what your schedule and workload are for the day. The objective is to plan what you will do and stick to the plan. If you have dedicated two hours to take photos, don't do anything else during that time, and don't allow yourself to be distracted unless it is a true emergency. 

Biting off more than you can chew is a surefire way to get discouraged easily, feel overwhelmed, or give up. Setting small achievable goals can help limit these feelings. You may currently have items that need to be listed but feel too overwhelmed to even begin. The key, and often the hardest part, is getting started. Pick up some items and get busy; once those items are photographed and listed, get some more items, and keep the momentum going. If you set small goals and consistently achieve them, you will feel productive and keep going.

eBay goes a lot faster if you work with like items in batches. Keep this in mind when sorting and storing unlisted inventory. For example, if you have a lot of sweaters, pick 10–20 for a batch. Prepare them all at once, photograph at once, and list at one time. You will be in the mode of working with that type of item and won't have to switch back and forth a lot. You can also use the Sell Similar feature on eBay so that information will carry over from one listing to another and you will only have to change small details, photos, and prices. eBay category, store category, item specifics, and the description will basically be the same.