Twelve tips for improving your altitude awareness

Stay current. Currency not only improves overall safety in skydiving and aviation in general, it also improves the sharpness of your altitude awareness. USPA currency requirements for various licenses should not be seen as good examples of how long to wait between jumps; rather, they are absolute limits.
Establish good habits. Check your altimeter on every jump you do after a successful canopy control check. Monitor your decision altitude and hard deck regardless of whether or not you have a good canopy—get used to what they look like. Fly a crisp, predictable pattern at exactly your planned altitudes whenever safety permits.
Use digital altimeters instead of analog. Analog dial altimeters, while dependable and often legitimately used in training for this reason, do not have the same level of accuracy as digital. In addition to parallax error, in the lower range the space between the “1” and the “0” only occupies the span of about a centimeter. In the landing pattern it is much more informative to see an actual number rather than decoding a needle pointed somewhere in that region.
Use a speaking audible. The regular rhythm and simple comprehensibility of speaking audibles make them invaluable tools for developing good altitude awareness during all stages of a skydive. You have to glance at a numeric altimeter to get the current altitude; a speaking audible tells it to you no matter what.
Use the ride to altitude. Familiarize yourself with what various altitudes look like; we refer to this as altitude picture. Glance out and guess the altitude. Try to guess when you arrive at certain thresholds that are important on a jump. Anticipate your audible or LED altimeter, looking out and trying to guess when it will indicate the next threshold. Train your eyes, train your mind.
Jump at different dropzones. The altitude picture looks different at different dropzones because of features of the terrain. It is much harder, for example, to tell your altitude when jumping over barren terrain such as a desert, snow-covered expanses, or a large body of water. Jumping at different dropzones helps to generalize your sense of altitude to adapt to a more diverse set of terrain.
Jump at different times of day. The altitude picture can look different depending on the time of day you jump. The darker it is, the more difficult it is to visually ascertain altitude; at night, in certain cases it can literally be impossible to tell how high up you are without the aid of instruments.
Do an occasional high pull. High pulls enable you to experience descent slowed down. Use the opportunity to better familiarize yourself with the characteristics of what different altitudes look like independent of your closing rate (e.g. ground rush near the bottom end on a freefall skydive).
Use non-technological cues. Take note of what altitude the cloud base is at when you are ascending in the plane and where it tops out. Be aware of how temperature changes with altitude on a particular day, or how much brighter it is higher up compared to lower down.
Seek out others with good altitude awareness. Altitude awareness varies—unfortunately sometimes greatly—from jumper to jumper. Seek out those with great experience who are considered by other experienced parachutists to be exceptional in the area of altitude awareness and speak to them about it; this will be evident, for example, in the consistency or predictability of their pull altitudes and the repeatability of their landing patterns, among other things.
Work in the sport. Those who display the best altitude awareness are often the same ones who work—or who at least have worked—in the sport for some length of time. Essentially, your development of altitude awareness in such a vocation is part of what they pay you to do, as it is critical for safe operations. Jumps like tandems give you plenty of time to develop and calibrate your altitude awareness.
Learn more about altitude awareness. You are already doing the work. FDS has a lot of good material discussing both the nature of altitude awareness as well as the various types of altimeters that can be used to improve it. Knowing more about it draws your attention to it naturally in the sky and can lead to higher-order awareness: an awareness of your own level of altitude awareness.

These materials are not a substitute for proper training by certified instructors. See, for example, the United States Parachute Association's Integrated Student Program, described in the Skydiver's Information Manual.