I used defines with IFCONST to optionally include code into the ROM.  I added a DEFINE_DEMO which results in reduced features and a different title screen in the output ROM.  If I comment out DEFINE_DEMO the output ROM is the full game.  This is very convenient for debugging and being able to easily enable and disable game features.

I recommend not just learning 6502 assembly, but also reading the dasm manual.  That's how I learned about using aliases with SET.  This allowed me to set aliases for my variables that are only in effect for a subroutine.  Some of the algorithms could get a bit complex and with variables like TEMP, TEMP2, TEMP3, and TEMP4 it can be very difficult to understand and debug.  Appropriate variable names makes things much easier to understand.