Employment Quetions?

Well Hello.

My cousin helped get a job as a REP/intake specialist(like a telemarketing company) .. i start Monday.. anyways i got worry about filling all the information online. like W-4 and I-9 like i didn't understand. i've never done taxes. im doing them for the first time next year. in w-4 its asks ''Total number of allowances you are claiming'' i put 0. i wasn't sure what to put. the this one '' Additional amount, if any, you want withheld from each paycheck'' i left it blank. and also this one "''{I claim exemption from withholding for 2013, and I certify that I meet both of the following conditions for exemption.
• Last year I had a right to a refund of all federal income tax withheld because I had no tax liability, and
• This year I expect a refund of all federal income tax withheld because I expect to have no tax liability.
If you meet both conditions, write “Exempt” here}''''''''' i just left it blank . im worry that it will affect me and some how i will have to pay a lot of money. and for the I-9 Form whats the " Admission Number"? i just put the USCIS 9 digit number. also i had to fill this online form the background check. so much information.well im going monday to start my 2 week training. ill get paid $10hr. Hopefully i didnt put nothing stupid . im just worry that it will affect me.

PS
I Hate Filling personal Stuff online