Repaying Student Loans in the US

[Monoriu]

We are doing some research into repaying student loans in the US.  My understanding is that the US adopt a pay as you go taxation system.  My question is, are student loan repayments witheld in the process?  If not, I assume that borrowers repay by separately writing a cheque to whatever agency is responsible for handing out the loans?

Thanks. 

[MadBurgerMaker]

Yeah I pay them online as just another bill.

E:  It goes through/to my loan servicer, which in my case (and a lot of others, I guess) is Great Lakes: https://en.wikipedia.org/wiki/Great_Lakes_Higher_Education_Corporation

[Admiral Yi]

The only time student loan payments are withheld from your paycheck is when you don't make payment (or some sort of arrangement to suspend payment) for 12 months.  Then your paycheck can be garnished by the Department of Education.