Know your organic chemistry. Typically organic chemistry is a prerequisite for biochemistry classes; if you had a rough time in "orgo," however, make sure to review and go over what you learned before you hit "biochem." The better you understand relationships between structure and function of organic compounds, the better you'll be able to make sense of the pathways you'll see in your biochemistry class.
Don't just memorize but try to understand as well. The better you understand what's going on --- what is being transformed to what and how --- the easier it will be to remember a pathway and make sense of what you see.
Practice drawing the pathways. Ultimately, this is probably the best way to get a handle on a complex pathway. Try drawing all the pathways you're expected to know; then go back and assess how far off you were --- and if need be, review the material then try drawing them again.
Make a mnemonic that will help you remember the names of the intermediates suggests Oregon State University. A mnemonic can be nearly anything --- it doesn't have to make sense; it just helps you remember the names of the intermediates in a pathway. Popular examples from biology and astronomy include "Deranged Kings Pour Coffee On Fairy Godmothers" (domain, kingdom, phylum, class, order, family, genus, species) and "Oh be a fine girl, kiss me" (for the order of the star classes on temperature/luminosity charts in astronomy). The best mnemonics are the ones you make up yourself, because they'll be the ones you're most likely to remember.
Find something that makes the material interesting to you. Maybe you're interested in the biology of cancer; in that case, you can relate what you're learning to cancer biology by thinking about the Warburg effect. Maybe you're interested in how poisons, such as cyanide, act inside the human body --- in that case, you could relate that to what you're learning by thinking about how cyanide inhibits the cytochrome c oxidase protein. Or maybe you can relate what you're learning about lactic acid fermentation and the Cori Cycle to your everyday life by thinking about what happens when you exercise. Cornell University recommends that whatever it may be, find something that makes the material interesting --- it will make it easier to learn.
Be prepared to spend plenty of time studying. Biochemistry is not the world's easiest subject --- it will take time to master. Drawing diagrams of the pathways is one of the best ways to remember them, but it's time-consuming as well.