Everybody wants nice and toned arms. Many downfalls of unexperienced trainers lead people to believe that the only way to more defined arms is to curl, curl, and curl.
Yes it is true that adding curls into a program can help in your quest, but centering a strength training routine around them is not the answer.
Stick to basic, compound movements like push ups, inverted rows, and chin ups. If you feel like doing more work at the end of your session, then by all means do a few sets of curls and pressdowns.
Use the "big" movements to help you reach your toned arm goals!