You are allowed to claim employment expenses as an itemized deduction (as is everyone else). These are claimed on Sch.A and Form 2106. On form 2106, you can take a "per diem" meals & incidental expenses deduction. There are a number of methods you can use: actual $ spent on meals, transportation worker rate ($38/day away from home), and per diem based on what cities you're in each day (very tedious calculation but usually yields a higher deduction than $38/day). From this amount, you must subtract any per diem allowance your employer provides that is not included in your wages (box 1 of W-2). The net is multiplied by 65%. You must be away from home overnight to claim any meal deductions for that day.
Once you figure your 2106, you carry the total to Sch.A, where it is reduced by 2% of your AGI to determine your allowed dedduction. If your total itemized deductions > your standard deduction, you itemize. If not, you just wasted a lot of time figuring out all your expenses.
Other employment expenses include: union dues, tools & equipment bought for work, work-related classes & books, phone calls home while on the road, work-related cell phone calls, travel expenses, showers, toiletries, etc. Any expense under $75 (except hotels) does not need a receipt, but you do need to be able to substantiate the date, place, & business relationship of the expense.