This is a question we hear often, how fast should I be going? There is not one size fits all answer to this question but we can talk about a good range to start. When it comes to waterskiing, you will see the pros going around buoys at around 32-36mph, now that is certainly not where you should start. When learning to get up on two skis, a child or smaller adult could be going as slow as 12-15mph, whereas a full sized adult on a slalom ski you will probably need to be going much faster and move into the 20-30mph range. The speed of skiing all has to do with your weight, your comfort out on the water, your experience, as well as the type of ski you may be using. Wider skis are generally best for slower speeds, and narrow skis are able to handle higher speeds.
Wakeboarding speed must also take the same considerations into account just like skiing: your weight, your comfort, your experience, and your board. The general rule of thumb for wakeboarding is 15-25pmh. Again, this is not necessary to learn and start getting your basic tricks down. Learning at slower speeds can help prevent painful crashes and help get your comfortable on the water. Going as slow as 12mph on a wakeboard can be beneficial to your learning process. When you get to the point where you are wanting to invert the wakeboard, this is when to increase the speed to give you a more firm surface to land on.