Private Ski Lessons
If you don't need the social element of group lessons and you can afford the fees, private instruction is, not surprisingly, the best bet. This is particularly true if you are the kind of person who likes the idea of going back to the same resort year after year: once you have found an instructor who is on your wavelength, you can book that same person every time you go.
In some resorts, private lessons are squeezed into the day at particular times, between classes that are taught by the same instructors. This is not always a particularly attractive arrangement - particularly if the rest of your party is expecting to meet for lunch at exactly the time your lessons crop up - so if it matters to you check before you commit yourself to a particular resort. In others, private lessons are much more important - so you are likely to find a much wider choice of timetables.
For more tips and advice on learning to ski: Teaching yourself to ski | Group ski lessons | Indoor ski slopes and dry slopes