If you're putting in a lot of miles:
1) firm saddle (not soft) that holds your sit bones properly and doesn't chafe your legs, as per previous poster - your height and weight are much less important than your rear-end architecture in picking a saddle
2) proper fit - having a bike whose geometry fits you, and finding a good saddle position position
3) good cycling shorts whose chamois covers what it needs to cover, and doesn't bunch up on you in crucial areas, etc.