Get a copy of the Job Announcement for your interest. The Departments usually list what they test on and what they are looking for under knowledge, Skills and Abilities.
Every police department uses a test they like to give.
All tests I have ever seen include, math, spelling, punctuation, logical deduction, reasoning.
One test gave you a picture. It said look at this picture for 5 min, do not take any notes. 5 min went by and they took the picture off the screen. They then handed out a sheet about the picture and asked 25 questions from that picture for you to identify.
Try looking at Hocus Focus, a testing of seeing items side by side with noted differences. Study word power in the Readers Digests at your local library.
The library also has study guides for police, firefighter etc or civil service job exams. Anything you do will help you to build a pattern of timing yourself at how long you have on each section to answer the questions.