Research, research, research - And then feel like an idiot
All aspects of your web site should be thoroughly examined, whether it is function, style, seo, usability, etc. Here is a perfect example, we have been using Canada Post to ship all our packages as the price is right but shipments to the USA take usually around 8 business days to get there (they say allow 9-12 days). So we have been looking at FedEx and other carriers and going through all the usual cost analysis stuff. What we didn't look at was Canada Post. On their web site we found that if we electronically prepare the documentation and customs information for them we will not only get a reduced price (which I knew about) but also the delivery times for the USA would go down to 5-9 days. That makes a HUGE difference for our customers. That 1 little piece of information was well worth the 3 hours it took of digging through the mess they call a web site.
I feel like an idiot (for posting this) but also for not exploring all the options. If it is looking on a web site, or calling your supplier, look for new suppliers, etc. you never know if there there is a better deal out there unless you look and ask. The 3-4 days we can knock off of shipping time to the USA could mean the difference between repeat business and no repeat business, and it is repeat business that will mean the difference between a sucessful store or a side line hobby.
This can be applied to all aspects of your business such as every year end take a look at the numbers and see where you can cut costs. Research other suppliers to make sure you are getting the best deal or ask you current supplier "is this the best you can do", reorganize your work day to cut down on the number of miles you have to drive or the time it takes to get to work, etc. And my #1 tip for the day; plan your to do list before you go to sleep every night, that alone will cut your work day by 30%.
I know this seems like common knowledge but everyone needs to be reminded of it sometimes.