Hi,
the rate usually depends on the city that you are going to. I use my local rates as a base and then multiply a factor to it. As an example, I multiply a lower factor for Bali than say Paris. However, logically, it is always higher than the local rates. The price you eventually charge, depending on the city, depends alot on the cost incurred, doing a shoot in that city. Again, as an example, Bali would be cheaper than Paris. Airfares to Bali are cheaper than Paris. Hotel lodging, transport and other daily costs are also cheaper in Bali.
I normally charge them by job, but if they require an additional day, then an additional charge is required.
Also, you have to work out your costings really carefully, if you intend to make the shoot profitable. Take note of hidden costs, like cab fares from the airport to your hotel and IDD phone calls among others. You might also want to consider getting a makeup artist, unless your clients are flying down the makeup artist, doing the makeup themselves or hiring a local makeup artists.
A common question I am asked by couples, is whether makeup will be provided and who will the makeup artist be.