A good memory for one. There is a lot of laws one has to remember. Nowadays they have programs to help, but you have to know what to look for. From there it depends on the type of law you want to go into. If you are talking trial law, then you need to be able to debate and think quickly to get answers from people on the stand.
To become a good lawyer you should know your subject matter, provide pro bono services, be respectful and honorable. In addition, having a good mentor that has had experience in the legal field also helps.