If dealing with an overseas-based literary agency is it normal to be charged for expenses incurred directly on the writer's behalf such as long-distance telephone calls, postage and handling, messengers, copying and approved legal expenses? And if so, how is it possible to gauge how many of these expenses are actually legitimate?
Agencies usually absorb the phone calls and postage & handling within the country; if they're incurring expenses such as messengers, overseas postage and legal reading on your behalf, they should be asking you first if you're happy to bear that cost. Most agencies will charge for photocopying but it should be clear in your agency agreement that this will happen. In fact, every possible charge to you should be contained in your agency agreement. If it's not, the agency really shouldn't be sending you a bill for anything you haven't requested or approved. And that's how you work out whether the expenses are legitimate or not.
There's a good checklist of what agents should and shouldn't be doing, plus a list of the top 20 dodgy US agents, on this website: http://www.sfwa.org/beware/twentyworst.html. You may also want to check out Preditors & Editors.