Chances are, you once learned jingles such as "I before e, except after c," and "Thirty days hath September...." Jingles use rhythm and rhyme to aid memory. Ancient Druidic bards memorized history by learning thousands and thousands of lines of poetry.
Acronyms and acrostics work best with lists. In school, you might have used the acronym HOMES to help you learn the Great Lakes, or the acrostic Every Good Boy Does Fine to learn the lines of the musical staff.
When you have to memorize a phone number, you probably use chunking to do it. Learning a random 10 digits is harder than learning an area code, a prefix and the last four digits together. This is why credit card companies and government agencies break important numbers into groups of no more than four characters and rarely more than four groups.
Songs, like poetry, can help you remember complex information. Almost everyone learns the alphabet song as a small child. In junior high or high school, you may have learned about the Battle of New Orleans from a song.
One of the most common visual tricks is the "walk a path" method. Pick a route you walk or drive frequently. Take an imaginary walk along the path. Each time you get to a different landmark, visualize one item or point associated with it.
Tony Buzon's mind maps use color, images, chunking and associations between ideas to help people memorize a lot of complicated material, fast.
The classic key to committing information to memory is repetition. Do it like a weight lifting workout---do lots of repetitions, in multiple sessions. Cover each area a few times every session.
Put the things you want to remember onto flash cards. Sort the cards into material you already know and material you want to learn. Take your flash cards everywhere and go through them whenever you have a few spare minutes.
Use a tape recorder. Say what you want to know and play it back everywhere you go, every time you get a chance.
Lastly, when you sleep your brain organizes the information and experiences from your day. Study the material immediately before you go to sleep; it will take you far less time to learn it.