Make sure your attention if focused on the material you want to remember. If you have other distractions going on around you - music playing, the TV on, kids talking, etc. - your mind won't be able to focus on the material. This will result in it being hard to remember what you've studied.
If you notice that you are having trouble with your memory, you may want to try running or riding a bicycle on a regular basis. Medical research has shown that running and bicycle riding stimulates the growth of new brain cells, which in turn, helps to improve a person's memory.
Try to avoid alcohol if you would like to improve your memory. It has been scientifically proven that alcohol kills the cells from the part of the brain that absorbs information. However, most research seems to prove that having one or two glasses of wine a day is okay for the memory.