every hair transplant surgon (including yourself) always says a person has to be a good candidate for hair transplant to be feasible and succesfull. what exactly do you mean and how do you define a good candidate?
A good candidate understands the process of balding and the limitations of a hair transplant surgery (where the transplant process works and does not work). The presence of realistic expectations reflects the supply/demand issues of the donor supply and this requires some prediction of your long term balding patterns. The concept of a Master Plan is critical in knowing that you can meet your goals. The rest is determined by the relationship between and good doctor and a patient willing to accept what transplants can and can not do.
All too often, patients who are 21 years old (too young) do not want to bald and they are not willing to really understand what they have to do (from taking medications to following the miniaturization mapping). It’s also worth noting that there are some things that might immediately disqualify you from a surgery: some forms of OCD like trichotillomania (until you have it under control), some forms of alopecia (we don’t want to transplant diseased hair that will just fall out again), etc.