The acronyms SAMPLE and AVPU are nothing more than mnemonics (memory aids for you) to remember what kinds of questions you need to ask your patients when assessing them and determining their mental status. AVPU is a quick and dirty method of a mental status check, it doesn't replace more in-depth methods of determining mental status. For "altered mental status" patients, AEIOU TIPS is the mnemonic that's used to remind you of the most common reasons why patients can be altered.
Probably the best method to practice doing patient assessments is to simply do patient assessments. I know that sounds strange, possibly even circular, but enlist your friends, family, even the dog. Just simply ask them to help you study for your EMT class. The dog probably won't give you much information, but it will probably like the attention and will be something you can at least talk to with a one-way conversation to get used to asking questions.