A good way to start is just working the problem through first, by hand, with paper and pencil. You have to know what you're doing step by step, before you can code it for the computer.
Originally Posted by alone2002dj
Note each step and put it down into one of three basic functions: Input, Processing, and Output.
Now work up a step by step pseudo code in semi-english (whatever your primary language is), that can easily be altered into C code, later.
While working on your pseudo code, don't worry about proper syntax for C, but do make your indentation show what the program flow of execution, will be.
for each customer
enter their bank balance
If (balance < 10000)
elseif (balance > 10000 && balance < 50000)
print "customer" and newline
Now refine your pseudo code, statement by statement, in valid C code, testing as you go with the compiler. Be sure your compiler's warning on turned on, and if you see an error or warning STOP and fix it. Nothing's worse than to have a whole program, which won't compile, and gives hundreds of errors.
For any further help, post your code, and tell us exactly what the problems are. We answer questions relating to C code, but we're not homework "dogs".