For me, I found that what had the biggest impact was just tracking. Keep track of how I am using my time, how much I spend on each task, how much I can get done in an hour, etc. There are apps and computer programs you can use for that — I suggest you try a few to see which one fits your work schedule the most.
Once you have the numbers on how your time is spent, figuring out ways to be more productive becomes much easier. You can start by isolating and eliminating time sinks. For example, I’d check my email several times during the day, and that added up to a lot of time wasted because I’d stop what I was doing to answer new emails. I switched to answering emails in clusters instead, so I could stay focused during the rest of the day.
It can also help you isolate tasks that you should probably automate. For example, if you spend a lot of time on design tasks that are fairly repetitive, using a tool like the fire door schedule software found at RapidSpec might help.