I previously worked at an early stage daily deals business so we were very operational. One of our major costs was the amount of time it took for our sales team to set up a deal with a merchant. One of our main focuses was to build internal tools to scale this part of our business. If we could reduce the time it took to set up a deal, we could run more deals and offer a better selection products to our customers.
Figure out how to scale the operational work. Build yourself tools that will automate parts of the business. Scaling customer support? Maybe offer a discussion forum so customers can help each other? Or at least build a help section that answers the most frequent support issues.
Just remember it's about scaling the process, not getting better at time management.
As a first time founder myself, I can agree that the amount of tasks that get thrown your way can be horrendous. Especially if you, like me, were used to being a developer where it was often encouraged that people not fuck with you for a solid 4-5 hours so you can do your thing.
I've started by taking advantage of to-do lists. I had always used them to some degree, but now I put EVERYTHING on my lists, and am constantly evaluating the priority. Most recently I've been using Trello (Kanban).
I can't really give you advice for the priorities because that really depends on your business, who you have working with you, and a number of other factors.
Additionally, this may not be applicable for you, but I have to block off a certain time of day to code. It isn't always the same time. It fluctuates from 430AM - 1030AM, to 9PM - 3AM. It isn't regular at all. But during that time I know coding is the ONLY thing I will address.
I block off my coding time because for me, it is the least unpredictable. I cannot predict what sort of customer support, deal work, or an infinite other amount of phone calls will come up. So the easiest way to handle it, for me, is to know that I have a certain part of my day (very early or very late) dedicated to code, and the operational issues and customer support can be handled in the middle.
My hardest problem has been feeling like the items I tackled that day were the right ones. I often go to sleep feeling like I should have focused on something more, and other things less. I suppose that is normal -- there is always room for improvement.