Q2: If I buy a Volt today (5/4/2012), when do I get the credit back?
A2: You claim the tax credit on your 2012 Federal Taxes. So you wont see the money until you get your refund in 2013 after youve filed your taxes.
Q3: I make $x dollars per year, have y kids, and $z mortgage, can I claim the full credit?
A3: This is one that you really need to calculate out. Be very careful with this as you may not get the full $7500 depending on your circumstance. The tax credit is non-refundable and does not carry over. Meaning you must claim it in one tax year, and you cant carry over any benefit into future years. IN General if you have $7500 in tax liabilities after all your deductions, you can claim the full credit. Someone making about $56,000 a year with only a standard deduction (no kids, mortgage etc) will generally be able to claim the full credit. However, if you have significant deductions from kids / house, etc you might run into trouble. On way of doing a quick check is to see how much you owed the IRS in taxes last year (assuming this year your tax circumstances didnt change materially). This is not the amount you paid or got refunded, but the total tax owed. (This is on Line 44 last year of your 1040)
If you hit AMT, sorry I cant help you. I dont know nearly enough about that. Ill let you know when I hit AMT