In General:
i.    Business expenses are deductible (162); personal expenses are not (262)
ii.    In practice, determining which expenses are deductible is largely a matter of matching them to deduction-granting Sections in the Code, but in interpreting those sections one must also understand the source and the general policies underlying the congressional decision to grant each specific deduction.  Courts view congressional decisions to treat an expenditure as deductible as a matter of legislative grace.  T/f, deductions are narrowly construed and only those items that qualify as one of the specific, statutorily authorized deductions may be deducted from GI in calculating AGI or from ADI in calculating taxable income.
iii.    The biggest and most important distinction are those items that are to be deducted when calculating GI (above the line) and those that are to be subtracted from AGI (below the line)
iv.    Important note:  62 does not grant anyone a deduction—it is only a discriminator of which deductions will be above the line and those that will not be above the line.  You have to find a provision in the code that actually grants the deduction.
v.    So here’s how it pans out:
Gross income
Minus “good” deductions (i.e., 62)
Adjusted gross income
Minus “bad” deductions (no provision collects them all)
Taxable income
vi.    You’d rather be an above the line deduction.  If you take the standard deduction, then your itemized deductions are worthless to you.  It’s an either/or proposition.  To the extent that you take the standard deduction, all the itemized deductions in the world don’t do you any good.