any kind of work you can think of... if somethings not working, TEMPORARILY put it aside and work on something else... if you see someone do a fancy trick, learn how to do it, and make it better... or think of different ways to use it...
for instance, i think i was talking to pablo when i came up with this one... you know how shiek, with her up b, can do the fancy edge-hog where you can just run off and she does the cool smokey stuff? well, i thought "i wonder if you could do that backwards" and i tried things out, i experimented, and then i figured out how to do it... then i showed someone else later (who has a much better shiek than i do) and he then took it to ANOTHER level and figured out a way to use it in a real match...
1. Definite major purpose
2. Constant improvement..
good formula... i think its called the demming's concept or something like that. its pretty handy when you're not necessarily trying to hardcore just train train train.. but more like... to understand the game more and build the competence and stuff... and of course... to give you more options... the way i see tricks and all that... its simply more options, and the more options you have, the less likely you are to be predicted... therefore you gain the mental advantage....
and yes, just keep at it... quitters never win, winners never quit (unless you're ken and have been doing it consistently forever but that doesn't count he's just retiring, lol)
EDIT: And since I will argue that I do training mode more than any two people in this thread together... ill share what i do with marth in training mode, i know you may not need it bryan, but this is just stuff i practice.
Comboing marth- since marth's easiest character to combo (imo) is...himself... do combos... then... create new ways to combo...with new moves
Tipper spacings through platforms- admittedly i only started this several days ago, but its of course very useful to know EXACTLY where you can stand to get tippers on what stages.... for instance, on PS you can tipper left or right on the platform by standing directly above the gray line thing...
Movement: since i strive to make my marth like tony j's (er... taj's) it requires a lot of movement practice (his is like perfect) and for me, i just try to do weird random movements and see if they might be useful to throw someone off
wavedash to attack- this one is probably best used by kuni i must say... of any marth... his marth is fast as in he can get in, tap you five or six times, then get out and you cant hit him... he uses he neutral a's so well... as for me i like using them to trick people into going one way (you know me, lol) so i can follow them (since i knew which way i wanted them to go) with a grab or f-smash if im too far away...
EDIT II: I NEED ONE MORE PERSON TO GO TO NEW MEXICO!!! (no kuni, not mexico)