things gets rehashed a lot. do a search and find a plethora of info. but in brief:
retaking classes shows you are serious, and that you CAN do the work. However, 2 pts:
If you didn't do THAT badly, you may want to take a different class which will show the same ability and drive, but will actually add to your knowledge base. Popular choices: calc, micro, macro, finance
Two buts:
1. not all schools are created equal. Community colleges, local state schools, some online programs might be considered sub-par. UC Berkeley and UCLA extensions get props, though are somewhat pricey.
2. Doing a class or two in isolation is not the same thing as juggling a full course load and doing well. Still, it shows you care and have some potential.