It is important that your beams receive adequate bearing over structural support posts.  An unbalanced or insufficient post beam connection could result in a deck collapse.  The more surface area the beam and post share the more balanced and evenly distributed the load can be transferred to the frost footings.  I Notching beams into posts is the strongest connection and is strongly recommended.  This system accommodates full bearing and laterally stabilizes the beam. 

Post beam connectors are available and can be effective in solidly anchoring beams to structural posts and resisting uplift from the wind.  Be especially careful where two or more beams intersect on top of a post or where a post is set at an angled intersection such as when building an octagon.  You may want to consider rotating the post to pick up a greater share of the beams bearing.