Get some help from teachers or tutors. Part of the problem many students have is the transition to more complicated and less defined math skills. College is fast-paced when compared to high school, so falling behind is easy. A tutor or help from the teacher can go a long way in learning those areas that are a bit confusing.
Read the textbook several times. College math requires more than the memorization of formulas that high schools depend on. The theory behind the formula is often required for success in college, and that can require reading the text several times.
Pay attention to the notes that are highlighted in textbooks. These are important key points that are required to learn college level math. Without these key points, many formulas, theories and mathematical ideas can be missed.
Write down notes in class. Whether the class is online or in a classroom, the teacher will write notes. These notes should always be copied, and there should be explanation notes based on lectures that aren't necessarily written by the teacher. The better the notes are, the easier they are to decipher later.
Practice. The best way to learn the math is to practice by using problems in the book and getting feedback on the problems when struggling. Whenever the answer is wrong and cannot be reworked to find the correct answer, take the problem to the teacher and ask for help.
Get reference materials. You can find many books on college-level maps at bookstores or libraries. The best reference materials are those that have simple explanations..