#ifs can be very useful, but code with lots of #ifs can be hard to read.
Get an editor which can "hide" the "inactive" code for you; eg, CodeWright.

Most compilers have an option which allows you to generate a listing of the pre-processed text as the compiler sees it; ie with all the #include files included, all the macros expanded and only the "active" conditional code in place.
This is invaluable for debugging problems with #ifs, #includes, and macros.

Some compilers allow you to retain the comments in this listing - which makes it much easier to read (unfortunately, Keil doesn't).