Hint :
Character Picking:
To make one of your 3 selected characters appear first during a match press and hold L at the versus screen for the 2nd character or hold R for the 3rd character.

New Costumes:
After highlighting a character on the character select screen press Y or A.

Get points without playing:
Go to training mode and select your characters. Instead of fighting, leave your dreamcast on overnight. Eventually, the points will start going higher and higher after a few minutes.

Defeating Abyss:
Use Cable to fight Abyss. In his first form, block his attacks and then press Y to shoot. Repeat until he dies. In his second form, keep away from him and press Y to shoot. Repeat till he dies. For his last form, use Cable's Hyper Viper. It takes off 90-95% of his life since you can do a 115-130 hit combo on him. Then finish him off with any attacks of your choice.

Cheaper hidden characters:
Exit and enter the shop screen several times and eventually the price of the hidden characters will be lower.

Same character selection:
To select the same character three times in arcade mode you must unlock everything in the shop and get your experience up to level 99.