If you plan to regularly exchange DTP files between Macintosh and Windows, you obviously have to choose a program existing on both platforms. See our pages on Quark Xpress, InDesign and PageMaker. Further to that, the three main points you should consider are:
The fonts used on the source computer must exist on the target computer. If it is not the case, there are some font transfer solutions, but they can't save all problems, mainly reflow problems (for an example, a main title on one line on the Mac reflows to two lines on the PC).
More, there is a strong consens amongst DTP professionals to only use Postscript fonts (Type 1) and not True Type. This could change with the recent agreement between Adobe and Microsoft about the new Open Type standard. Anyway, there could be a pretty long transition period, as many users will want to protect their huge investments in fonts.
Problems often occur when a Type 1 font bears the same name as a True Type font. More, some True Type fonts are not coded with a great care.
For the time being, the real solution is to define a set of Type 1 fonts existing on both platforms, preferably from the same vendor, and to stick with it. Some vendors propose fonts CD on Mac and PC. You should consider these offers.
The main problems with included graphics come from two formats: Pict files from the Macintosh and WMF (Windows metafiles) from the PC (sometimes also from BMP files). All DTP professionals agree using only Tiff files (bitmap graphics) or EPS files (vector graphics). You will also avoid problems using uncompressed files.
When you create DTP files on the Macintosh, you should be aware that if your files are to be opened under Windows,there are still more "illegal" characters on the PC side than on the Macintosh (which only prohibits ':'). Think it twice before using bullets, slashes, '<', '>', '©', etc.
In the other direction, the file length is still limited to 31 characters. More, if the files are to be put on a CD burnt in the ISO 9660 format, the Macintosh will still only see the short filenames and not the long ones.
What we said above holds generally true and applies to all professionnal packages (InDesign, Xpress, PageMaker). In this context, we should also mention MS-Publisher. While Publisher presents itself as a "light" layout program and only exists on the PC (which tells a lot about the orientation of its publisher), it often happens that professional DTPists get MS-Publisher files from customers.
What we said above (printing to a Postscript printer and going the PDF route with DIstiller) also applies to MS-Publisher. This is often the only good solution if the customer really did a lot of work and doesn't want to pay the price to redot everything.
PageMaker 7 for Windows includes a program to convert the MS-Publisher files. The tool doesn't exist in the Macintosh package. The result can then be opened in PM7 or in InDesign. There is often a lot work to do to recreate the pages, but sometimes it is a good working solution.