Your pay schedule depends on what type of funding you have. For most GSI/RA positions, you'll get paid in monthly installments at the beginning of each month (don't count on it being deposited to your bank before the 8th). Department fellowships get paid in lump sums at the beginning of the semester, while NSF fellowships are disbursed monthly like GSI/RA stipends. Note that electronic fund transfers for fellowships and GSI positions differ, so be sure to set them up separately, if you don't want to have to go fetch a paper check each month.
Pay attention to whether or not tax is withheld– it's not from fellowships, and can be a large surprise when it comes to tax time in April (~2600 on federal, ~900 on state for an NSF stipend in 2010).
If you should run low on funds and need $ right away for miscellaneous expenses (the payroll office has been known to mess up pay checks from time to time), note that the university offers $775 emergency loans with 0 interest for 60 day periods, with a $20 application fee. Go to 212 Sproul to fill out the form between 9am-12:15pm M-Th, and pick up your check by 1 the same day!