Practice.

Having macros for every single skill on every possible target is very uh... space inefficient and will only be worse when Crystal Tower comes out and you have to worry about 24 people total. You just need to practice with more people.

I haven't used them but many people speak highly of the mouseover target macros ( /ac Cure <mo> , for example) so you might want to try those out. You just have to hover over someone's name in the pt list and hit the macro to start casting on them.