Speculative principles refer to the concept of speculative reasoning. The idea behind it is to establish theories and provide ideas based on sound logic and detached from specific situations. Speculative principles want to establish firm universals and an example of that can be found in logic where it established the non-contradiction clause.
Practical principles is more active and involved and much less theoretical and tries to deal with existing problems in praxis, not just deal with theoretical problems. It has been thoroughly analyzed by those like Kant who discussed moral reasoning when deciding how to act in everyday situations.