Make sure scissors are ergonomic and will fit comfortably in your hand, as you will be holding these bad boys for quite a while. With time, these scissors will get very sticky, so get a pair that will clean easily, or buy two pairs so you can switch between them.
There are many types of scissors you can buy; some are spring-loaded, some not. Beginners often go for spring-loaded ones because they seem quicker.
However, a lot of trimmers recommend Chikamasa scissors—these are not spring-loaded and might take a day or two to get used to, but you will soon notice the precision and speed they provide.