In C, at a much simpler level, consider the following;
- Use #pragma pack(1) to byte align your structures
- Use unions where a structure can contain different types of data
- Use bit fields rather than ints to store flags and small integers
- Avoid using fixed length character arrays to store strings, implement a string pool and use pointers.
- Where storing references to an enumerated string list, e.g. font name, store an index into the list rather than the string
- When using dynamic memory allocation, compute the number of elements required in advance to avoid reallocs.