Docking scores are most often expressed as binding enthalpy. This means, the amount of energy that the system consumes to perform such a binding action is calculated. Now, as binding should should free energy rather than consume it you are looking for the most negative number (often kcal/mol or kJ/mol).

There are some things to consider besides the docking score itself:

• is the way your ligand is bound in the pocket by docking actually reasonable (no clashes, etc.)?
• did you generate enough poses so that it is oriented correctly (otherwise it would show a worse score than could actually be achieved)?
• do you have any biological data (e.g. a known inhibitor that you docked as well; as a general rule, it is always good to have controls) to support your conclusions?