This is kind of a general question, so I'm unsure exactly how to answer it. If you're using the hybridization model, the sigma (σ) bonds are always from the hybridized atomic orbitals on the central atom, and the pi (π) bonds, if any, are from the extra, unused p-orbitals, if any.
For example, in a nitrate ion, there are three things attached to the central nitrogen: one doubly-bonded oxygen and two singly bonded oxygens. The bonding orbitals on the central atom are the three sp2 hybrid orbitals, which form three σ bonds, one pointing toward each O atom, and the perpendicular p-orbital that is bound to one of the p-orbitals on one of the oxygen atoms. In this polyatomic ion, the π bond moves around from O atom to O atom, giving us three resonance structures when you're using a Lewis dot diagram.
I'm not sure what your question was, but I hope that helps.