Before we really start with this, keep in mind that your accountant is one of your best friends. He or she can save you a fortune (for a nominal fee) and can evenkeep you out of prison if you should happen to make an error (and it happens to the best of us). Their word should be trusted above all others, but the following is some good general advice that you would be wise to bring up with them around tax time. If all else fails, it is better to ask a question and get a no than it is to leave money on the table for life.
First off, anything which you need to buy or pay for in order to further your business goals is likely to be tax deductible. If you need to buy your own truck, your own overalls, your own tools, deduct them. And while only a professional can tell you how to schedule your deductions (some people deduct in the year they purchased an item, while some other people deduct a durable item like a truck over several years), it would be a serious folly not to deduct them at all. Itemizing is a bit of a pain, but it is a pain with a pay off down the line.
After all, when you deduct a lot of different things, you lower the amount of taxable income you appear to have made. This can be good for helping your kids get financial aid for school, for helping you invest more into your business through getting tax refunds, and it can be a real boon if you were afraid of not being able to pay all you might have owed.