At first glance, Bright Man's signature weapon (Bright Stopper) appears to be fired off at random. However, Bright Stopper is actually controlled by how much health he has remaining; after taking 12, 20 and 24 uncharged shots worth of damage, he uses it. at 11, 19 and 23 Health, fire a charged shot (or 2 consecutive uncharged shots) at him when hes shooting at you. If done correctly, Bright Man will be unable to use the Bright Stopper!
Toad Man is probably the easiest boss in the game. If you know how to fight him, he won't even attack.
All you have to do is shoot him with your m.buster. When you do that, he'll try to jump on top of you. Just run under him, and when he lands, keep shooting him. Repeat until he's defeated.
Toad Man (Use arm cannon; fire constantly and he won't hit you with the Rain Flush)
Bright Man (Use Rain Flush)
Pharaoh Man (use Flash Stopper)
Ring Man (Use Pharaoh Shot. The timing of your leaps is the key.)
Dust Man (Use arm cannon. Jump straight up when he fires the Dust Crusher at you, and when the shot splits all the pieces will miss you.)
Skull Man (Use Dust Crusher; the Ring Boomerang will cut through his shield (as noted by DocLight).)
Dive Man (Use Dust Crusher and Skull Barrier)
Drill Man (Use Dive Missiles)