If you aren't doing hires graphics, you don't have to mess with the screen memory directly. You can just call the ROM routines which has the nice side effect of working with 40- or 80-columns automatically. If you are doing hires graphics you are going to use a lookup table regardless as doing the multiplication to get the base address of a particular scanline is far too slow. You can, one time, either make a table manually, which you can use forever, or you can write a short routine that counts from 0 to 191, stick 0 in X and the scanline number in A and JSR $F411. It'll leave the base address of the scanline in $36 and $37. Which you can stick in your table.

As in other comments, if you are specifically interested in the Apple II line, the Assembly Lines books by Roger Wagner is fantastic.

Also, if you can find it Sandy Mossberg's Disassembly Lines articles in Nibble magazine were great too. Start with Assembly Lines, then read the Disassembly Lines and you'll be quite expert.