Students consolidating federal loans can do so through the Department of Education's website at Loan Consolidation.ed.gov, by phone at (800) 557-7392 or by downloading a paper application at LoanConsolidation.ed.gov/borrower/bapply.html and mailing it in. Almost all types of federal loans can be consolidated. Borrowers should have loan account numbers, estimated payoff dates and contact information for each of their loans' holders ready. Those seeking consolidation should also review their repayment options at StudentAid.ed.gov, so they're prepared to pick the proper repayment plan.
Once the application is submitted, the federal government estimates that it takes 60 to 90 days to officially complete the consolidation process.
Consolidating private loans works in a similar fashion, as far as paperwork goes. The difference is you'll need to apply through a private lender. Some are better than others, so make sure to look at the varying terms of each one -- staying away from charges or origination fees and checking the maximum interest rate so you won't get burned down the road. Most also have limits on how much you can consolidate. Know that you might need a higher credit score if you want the best rates without a co-signer.