Leslie that's a pretty broad question, but I will try to respond to all what the question implies.
The first important thing is to have the theorical capacity of piles in compression and tension. They are of course different, because in compression you have point-bearing capacity plus friction...
First to start, it is important that you know that predictions on bearing capacity using SPT are only moderately reliable, principally due to some inconsistencies in SPT test procedures.
Furthermore, the standard penetration test are not too good for predict pile capacities in cohessive soils...
