Don't make any assumptions about the architecture that your program will run on. If you have to go into variables with a different type than the one with which they were declared make sure you do so in a portable way.

So, for instance, if you want the lower 8 bits of an int don't declare a pointer to a character and then lift out the byte, but do (value & 0xff) instead.

That way if you move your program to a big endian machine it will still work. Storing pointers in ints assumes that pointers and ints are the same size, which is definitely not always the case.

So store pointers in a space sizeof(whatevertype*) rather than sizeof(int).