Take the sample mechanical aptitude tests. Score them and see how well you did. This will give you a starting point on the things you need to work on and what you have learned really well.
Print out pictures of the various tools that you will need to know and glue or tape them onto 3 by 5 index cards. Turn the card over and write the name of the tool and its purpose for each flash card.
Go through the tool flash cards until you have them memorized.
Write the names of the types of pulleys that you need to know for your aptitude tests. Get a sheet of paper and mix up the flash cards. For each pulley name, write on your paper the purpose and how the pulley functions. You can write this information for each pulley on the back of the correct flash card for a quick reference.
Print out 2 pictures of an electrical circuit. On one copy of the electrical circuit, write "Master Copy" at the top. Write in all of the parts and purposes of the electrical circuit. Test yourself on the second copy. Write in all of the different parts and their functions. Check your test copy against your master copy.
Study and practice as much as you can until your aptitude test. Make sure you get adequate sleep the night before you take your test.