I prepared tax returns for Realtors for over 10 years, and one of the things I've found is that many agents don't know what's deductible, so to help, I've created a list. Not all items on the list will always be a tax deduction, but if the expenditure is related to your work, it very well may be, but it depends.
For example, on the list is "Education". As a real estate agent, if you purchase classes that are directly related to your work, then it's almost certainly tax deductible. But if you took a class in glassblowing, for example, you may have a hard time justifying it's tax deduction, because it is not really related to your work as a real estate agent.
The IRS (and the State of Hawaii) generally allow deductions for expenditures that are "ordinary and necessary". Please feel free to share this list with your tax preparer as a tool for discussing your own tax situation.